Why do some white blood cells have lobed nuclei?

Why do some white blood cells have lobed nuclei?

We are searching data for your request:

Forums and discussions:
Manuals and reference books:
Data from registers:
Wait the end of the search in all databases.
Upon completion, a link will appear to access the found materials.

Several types of white blood cells (eg Neutrophils) have lobed nuclei. Is this for a functional reason? I have seen people refer to structural differences in the lobes as indicative of problems, but I have not been able to find why the nuclei form into lobes in the first place. Is this known?

Why do some white blood cells have lobed nuclei? - Biology

Using the 10X objective lens you can see individual cells and tell the difference between red and white blood cells. You can even see platelets if you know what to look for. The platelets on this image are very faint, but you can see them in the image below.

Most of the cells you see here are erythrocytes or red blood cells. They are small and don't have a nucleus. They are thin in the middle, and look like red doughnuts in this image. The leukocytes (white blood cells) are larger than red blood cells and they have nuclei that stain dark purple. Many of the white blood cells have segmented nuclei, meaning that the nucleus is pinched into two or more smaller parts that are still connected to each other (sort of like when you twist one of those long balloons to make a sculpture). Can you find the white blood cell in this image? Its nucleus has two segments.

The red blood cells in this image are stacked up on top of each other. We included it to show you what an unacceptable smear looks like! But it does have the advantage of including two kinds of white blood cell that are different from the one seen in the image above. The leukocyte on the left has many very dark granules in its cytoplasm. The granules are so dark that you can't see the nucleus. The leukocyte on the right has a two-lobed nucleus and reddish-orange granules in its cytoplasm. Consult your textbook to find out what they are.

What is Palmately lobed?

Pinnately lobed leaves have the lobes arranged on either side of a central axis like a feather. Palmately lobed leaves have the lobes spreading radially from a point, like fingers on a hand. Leaves divided into individual leaflets. Leaflets are distinguished from leaves in that there is no bud at the base.

Subsequently, question is, what is a lobed leaf? Noun. 1. lobed leaf - a leaf having deeply indented margins. foliage, leaf, leafage - the main organ of photosynthesis and transpiration in higher plants.

In this manner, what is lobed?

having a lobe or lobes lobate. Botany. (of a leaf) having lobes or divisions extending less than halfway to the middle of the base.

What does a lobed leaf look like?

Lobed leaves have distinct rounded or pointed projections, while unlobed leaves do not. Some lobed leaves are pinnate, meaning the lobes are located along a central axis, while others are palmate, meaning they radiate from a single point.


The name "white blood cell" derives from the physical appearance of a blood sample after centrifugation. White cells are found in the buffy coat, a thin, typically white layer of nucleated cells between the sedimented red blood cells and the blood plasma. The scientific term leukocyte directly reflects its description. It is derived from the Greek roots leuk- meaning "white" and cyt- meaning "cell". The buffy coat may sometimes be green if there are large amounts of neutrophils in the sample, due to the heme-containing enzyme myeloperoxidase that they produce.


All white blood cells are nucleated, which distinguishes them from the anucleated red blood cells and platelets. Types of leukocytes can be classified in standard ways. Two pairs of broadest categories classify them either by structure (granulocytes or agranulocytes) or by cell lineage (myeloid cells or lymphoid cells). These broadest categories can be further divided into the five main types: neutrophils, eosinophils, basophils, lymphocytes, and monocytes. [2] These types are distinguished by their physical and functional characteristics. Monocytes and neutrophils are phagocytic. Further subtypes can be classified.

Granulocytes are distinguished from agranulocytes by their nucleus shape (lobed versus round, that is, polymorphonuclear versus mononuclear) and by their cytoplasm granules (present or absent, or more precisely, visible on light microscopy or not thus visible). The other dichotomy is by lineage: Myeloid cells (neutrophils, monocytes, eosinophils and basophils) are distinguished from lymphoid cells (lymphocytes) by hematopoietic lineage (cellular differentiation lineage). [6] Lymphocytes can be further classified as T cells, B cells, and natural killer cells.

    : releases antibodies and assists activation of T cells :
      + Th (T helper) cells: activate and regulate T and B cells + cytotoxic T cells: virus-infected and tumor cells. : bridge between innate and adaptive immune responses phagocytosis : Returns the functioning of the immune system to normal operation after infection prevents autoimmunity


    Neutrophils are the most abundant white blood cell, constituting 60-70% of the circulating leukocytes, [4] and including two functionally unequal subpopulations: neutrophil-killers and neutrophil-cagers. They defend against bacterial or fungal infection. They are usually first responders to microbial infection their activity and death in large numbers form pus. They are commonly referred to as polymorphonuclear (PMN) leukocytes, although, in the technical sense, PMN refers to all granulocytes. They have a multi-lobed nucleus, which consists of three to five lobes connected by slender strands. [9] This gives the neutrophils the appearance of having multiple nuclei, hence the name polymorphonuclear leukocyte. The cytoplasm may look transparent because of fine granules that are pale lilac when stained. Neutrophils are active in phagocytosing bacteria and are present in large amount in the pus of wounds. These cells are not able to renew their lysosomes (used in digesting microbes) and die after having phagocytosed a few pathogens. [10] Neutrophils are the most common cell type seen in the early stages of acute inflammation. The average lifespan of inactivated human neutrophils in the circulation has been reported by different approaches to be between 5 and 135 hours. [11] [12]


    Eosinophils compose about 2-4% of the WBC total. This count fluctuates throughout the day, seasonally, and during menstruation. It rises in response to allergies, parasitic infections, collagen diseases, and disease of the spleen and central nervous system. They are rare in the blood, but numerous in the mucous membranes of the respiratory, digestive, and lower urinary tracts. [9]

    They primarily deal with parasitic infections. Eosinophils are also the predominant inflammatory cells in allergic reactions. The most important causes of eosinophilia include allergies such as asthma, hay fever, and hives and also parasitic infections. They secrete chemicals that destroy these large parasites, such as hookworms and tapeworms, that are too big for any one WBC to phagocytize. In general, their nucleus is bi-lobed. The lobes are connected by a thin strand. [9] The cytoplasm is full of granules that assume a characteristic pink-orange color with eosin staining.


    Basophils are chiefly responsible for allergic and antigen response by releasing the chemical histamine causing the dilation of blood vessels. Because they are the rarest of the white blood cells (less than 0.5% of the total count) and share physicochemical properties with other blood cells, they are difficult to study. [13] They can be recognized by several coarse, dark violet granules, giving them a blue hue. The nucleus is bi- or tri-lobed, but it is hard to see because of the number of coarse granules that hide it.

    They excrete two chemicals that aid in the body's defenses: histamine and heparin. Histamine is responsible for widening blood vessels and increasing the flow of blood to injured tissue. It also makes blood vessels more permeable so neutrophils and clotting proteins can get into connective tissue more easily. Heparin is an anticoagulant that inhibits blood clotting and promotes the movement of white blood cells into an area. Basophils can also release chemical signals that attract eosinophils and neutrophils to an infection site. [9]


    Lymphocytes are much more common in the lymphatic system than in blood. Lymphocytes are distinguished by having a deeply staining nucleus that may be eccentric in location, and a relatively small amount of cytoplasm. Lymphocytes include:

      make antibodies that can bind to pathogens, block pathogen invasion, activate the complement system, and enhance pathogen destruction. :
        + helper T cells: T cells displaying co-receptorCD4 are known as CD4+ T cells. These cells have T-cell receptors and CD4 molecules that, in combination, bind antigenic peptides presented on major histocompatibility complex (MHC) class II molecules on antigen-presenting cells. Helper T cells make cytokines and perform other functions that help coordinate the immune response. In HIV infection, these T cells are the main index to identify the individual's immune system integrity. + cytotoxic T cells: T cells displaying co-receptor CD8 are known as CD8+ T cells. These cells bind antigens presented on MHC I complex of virus-infected or tumour cells and kill them. Nearly all nucleated cells display MHC I. possess an alternative T cell receptor (different from the αβ TCR found on conventional CD4+ and CD8+ T cells). Found in tissue more commonly than in blood, γδ T cells share characteristics of helper T cells, cytotoxic T cells, and natural killer cells.


      Monocytes, the largest type of WBCs, share the "vacuum cleaner" (phagocytosis) function of neutrophils, but are much longer lived as they have an extra role: they present pieces of pathogens to T cells so that the pathogens may be recognized again and killed. This causes an antibody response to be mounted. Monocytes eventually leave the bloodstream and become tissue macrophages, which remove dead cell debris as well as attack microorganisms. Neither dead cell debris nor attacking microorganisms can be dealt with effectively by the neutrophils. Unlike neutrophils, monocytes are able to replace their lysosomal contents and are thought to have a much longer active life. They have the kidney-shaped nucleus and are typically agranulated. They also possess abundant cytoplasm.

      Some leucocytes migrate into the tissues of the body to take up a permanent residence at that location rather than remaining in the blood. Often these cells have specific names depending upon which tissue they settle in, such as fixed macrophages in the liver, which become known as Kupffer cells. These cells still serve a role in the immune system.

      The two commonly used categories of white blood cell disorders divide them quantitatively into those causing excessive numbers (proliferative disorders) and those causing insufficient numbers (leukopenias). [14] Leukocytosis is usually healthy (e.g., fighting an infection), but it also may be dysfunctionally proliferative. WBC proliferative disorders can be classed as myeloproliferative and lymphoproliferative. Some are autoimmune, but many are neoplastic.

      Another way to categorize disorders of white blood cells is qualitatively. There are various disorders in which the number of white blood cells is normal but the cells do not function normally. [15]

      Neoplasia of WBCs can be benign but is often malignant. Of the various tumors of the blood and lymph, cancers of WBCs can be broadly classified as leukemias and lymphomas, although those categories overlap and are often grouped as a pair.


      A range of disorders can cause decreases in white blood cells. This type of white blood cell decreased is usually the neutrophil. In this case the decrease may be called neutropenia or granulocytopenia. Less commonly, a decrease in lymphocytes (called lymphocytopenia or lymphopenia) may be seen. [14]


      Neutropenia can be acquired or intrinsic. [16] A decrease in levels of neutrophils on lab tests is due to either decreased production of neutrophils or increased removal from the blood. [14] The following list of causes is not complete.

      • Medications - chemotherapy, sulfas or other antibiotics, phenothiazenes, benzodiazepines, antithyroids, anticonvulsants, quinine, quinidine, indomethacin, procainamide, thiazides
      • Radiation
      • Toxins - alcohol, benzenes
      • Intrinsic disorders - Fanconi's, Kostmann's, cyclic neutropenia, Chédiak–Higashi
      • Immune dysfunction - disorders of collagen, AIDS, rheumatoid arthritis
      • Blood cell dysfunction - megaloblastic anemia, myelodysplasia, marrow failure, marrow replacement, acute leukemia
      • Any major infection
      • Miscellaneous - starvation, hypersplenism

      Symptoms of neutropenia are associated with the underlying cause of the decrease in neutrophils. For example, the most common cause of acquired neutropenia is drug-induced, so an individual may have symptoms of medication overdose or toxicity. Treatment is also aimed at the underlying cause of the neutropenia. [17] One severe consequence of neutropenia is that it can increase the risk of infection. [15]


      Defined as total lymphocyte count below 1.0x10 9 /L, the cells most commonly affected are CD4+ T cells. Like neutropenia, lymphocytopenia may be acquired or intrinsic and there are many causes. [15] This is not a complete list.

      • Inherited immune deficiency - severe combined immunodeficiency, common variable immune deficiency, ataxia-telangiectasia, Wiskott–Aldrich syndrome, immunodeficiency with short-limbed dwarfism, immunodeficiency with thymoma, purine nucleoside phosphorylase deficiency, genetic polymorphism
      • Blood cell dysfunction - aplastic anemia
      • Infectious diseases - viral (AIDS, SARS, West Nile encephalitis, hepatitis, herpes, measles, others), bacterial (TB, typhoid, pneumonia, rickettsiosis, ehrlichiosis, sepsis), parasitic (acute phase of malaria)
      • Medications - chemotherapy (antilymphocyte globulin therapy, alemtuzumab, glucocorticoids)
      • Radiation
      • Major surgery
      • Miscellaneous - ECMO, kidney or bone marrow transplant, hemodialysis, kidney failure, severe burns, celiac disease, severe acute pancreatitis, sarcoidosis, protein-losing enteropathy, strenuous exercise, carcinoma
      • Immune dysfunction - arthritis, systemic lupus erythematosus, Sjögren syndrome, myasthenia gravis, systemic vasculitis, Behcet-like syndrome, dermatomyositis, granulomatosis with polyangiitis
      • Nutritional/Dietary - alcohol use disorder, zinc deficiency

      Like neutropenia, symptoms and treatment of lymphocytopenia are directed at the underlying cause of the change in cell counts.

      Proliferative disorders

      An increase in the number of white blood cells in circulation is called leukocytosis. [14] This increase is most commonly caused by inflammation. [14] There are four major causes: increase of production in bone marrow, increased release from storage in bone marrow, decreased attachment to veins and arteries, decreased uptake by tissues. [14] Leukocytosis may affect one or more cell lines and can be neutrophilic, eosinophilic, basophilic, monocytosis, or lymphocytosis.


      Neutrophilia is an increase in the absolute neutrophil count in the peripheral circulation. Normal blood values vary by age. [15] Neutrophilia can be caused by a direct problem with blood cells (primary disease). It can also occur as a consequence of an underlying disease (secondary). Most cases of neutrophilia are secondary to inflammation. [17]

      • Conditions with normally functioning neutrophils – hereditary neutrophilia, chronic idiopathic neutrophilia (chronic myelogenous (CML)) and other myeloproliferative disorders[18]


      A normal eosinophil count is considered to be less than 0.65 × 10 9 /L. [15] Eosinophil counts are higher in newborns and vary with age, time (lower in the morning and higher at night), exercise, environment, and exposure to allergens. [15] Eosinophilia is never a normal lab finding. Efforts should always be made to discover the underlying cause, though the cause may not always be found. [15]

      The complete blood cell count is a blood panel that includes the overall WBC count and the white blood cell differential, a count of each type of white blood cell. Reference ranges for blood tests specify the typical counts in healthy people.

      TLC- (Total leucocyte count): Normal TLC in an adult person is 6000–8000 WBC/mm^3 of blood.

      DLC- (Differential leucocyte count): Number/ (%) of different types of leucocytes per cubic mm. of blood.

      Below are blood reference ranges for various types leucocytes/WBCs. [19]


      Neutrophils naturally have three or four nuclear lobes, but there are cases in which they can have more. Studies have shown that people who do not have enough vitamin B12 or folic acid have neutrophils that are hypersegmented, meaning the neutrophils have more than four lobes in the nucleus.

      A similar observation was made in people who did not have enough iron in their bodies. A lack of iron leads to anemia, which causes a feeling of weakness in the body. The journal “Pediatric Hematology and Oncology” reported that 81 percent of children who were iron deficient had hypersegmented neutrophils. Among healthy children, only 9 percent had hypersegmented neutrophils.

      Why do some white blood cells have lobed nuclei? - Biology


      This granulocyte has very tiny light staining granules (the granules are very difficult to see). The nucleus is frequently multi-lobed with lobes connected by thin strands of nuclear material. These cells are capable of phagocytizing foreign cells, toxins, and viruses.
      When taking a Differential WBC Count of normal blood, this type of cell would be the most numerous. Normally, neutrophils account for 50-70% of all leukocytes. If the count exceeds this amount, the cause is usually due to an acute infection such as appendicitis, smallpox or rheumatic fever. If the count is considerably less, it may be due to a viral infection such as influenza, hepatitis, or rubella.

      This granulocyte has large granules (A) which are acidophilic and appear pink (or red) in a stained preparation. This micrograph was color enhanced to illustrate this feature. The nucleus often has two lobes connected by a band of nuclear material. (Does it looks like a telephone receiver?) The granules contain digestive enzymes that are particularly effective against parasitic worms in their larval form. These cells also phagocytize antigen - antibody complexes.

      These cells account for less than 5% of the WBC's. Increases beyond this amount may be due to parasitic diseases, bronchial asthma or hay fever. Eosinopenia may occur when the body is severely stressed.


      The basophilic granules in this cell are large, stain deep blue to purple, and are often so numerous they mask the nucleus. These granules contain histamines (cause vasodilation) and heparin (anticoagulant).

      In a Differential WBC Count we rarely see these as they represent less than 1% of all leukocytes. If the count showed an abnormally high number of these cells, hemolytic anemia or chicken pox may be the cause.

      The lymphocyte is an agranular cell with very clear cytoplasm which stains pale blue. Its nucleus is very large for the size of the cell and stains dark purple. (Notice that the nucleus almost fills the cell leaving a very thin rim of cytoplasm.) This cell is much smaller than the three granulocytes (which are all about the same size). These cells play an important role in our immune response. The T-lymphocytes act against virus infected cells and tumor cells. The B-lymphocytes produce antibodies.

      This is the second most numerous leukocyte, accounting for 25-35% of the cells counted in a Differential WBC Count. When the number of these cells exceeds the normal amount, one would suspect infectious mononucleosis or a chronic infection. Patients with AIDS keep a careful watch on their T-cell level, an indicator of the AIDS virus' activity.

      This cell is the largest of the leukocytes and is agranular. The nucleus is most often "U" or kidney bean shaped the cytoplasm is abundant and light blue (more blue than this micrograph illustrates). These cells leave the blood stream (diapedesis) to become macrophages. As a monocyte or macrophage, these cells are phagocytic and defend the body against viruses and bacteria.

      These cells account for 3-9% of all leukocytes. In people with malaria, endocarditis, typhoid fever, and Rocky Mountain spotted fever, monocytes increase in number.

      The background cells in this micrograph are erythrocytes (red blood cells). These cells are non-nucleated, biconcave discs that are filled with hemoglobin. The primary function of these cells is to carry oxygen from the lungs to the body cells.
      Woman usually have 4-5 million erythrocytes per cubic millimeter of blood, men have 5-6 million. If this number is considerably higher, polycythemia may be the cause. If the number is considerably less, the person has anemia.

      Sickle cell anemia is an inherited condition which results in some erythrocytes being malformed. The gene for this condition causes the hemoglobin to be incorrectly formed, which in turn causes some erythrocytes to take on a crescent shape. These cells are not able to carry adequate amounts of oxygen to cells.

      Platelets, which are cell fragments, are seen next to the "t's" above. (Many of the other micrographs on this page contain them as well.) Platelets are important for proper blood clotting.
      Each cubic millimeter of blood should contain 250,000 to 500,000 of these. If the number is too high, spontaneous clotting may occur. If the number is too low, clotting may not occur when necessary.

      Why do some white blood cells have lobed nuclei? - Biology

      Blood provides a mechanism by which nutrients, gases, and wastes can be transported throughout the body. It consists of a number of cells suspended in a fluid medium known as plasma. Serum refers to plasma after clotting factors and fibrin have been removed.

      Peripheral Blood Smear

      The cells of the blood are important because they are a readily accessible population whose morphology, biochemistry, and ecology may give indications of a patient's general state or clues to the diagnosis of disease. For this reason, the complete blood count (CBC) and the differential white cell count are routinely used in clinical medicine. It is very important to be able to recognize normal blood cells and to distinguish pathological cells from the normal variants.

      The identification of blood elements is based primarily on observations of the presence or absence of a nucleus and cytoplasmic granules. Other helpful features are cell size, nuclear size and shape, chromatin appearance, and cytoplasmic staining. The chart at the end of this section explains what to look for in the effort to identify the component cells of a blood smear.

      Component Cell of the Blood Smear

      A blood smear is created by placing a drop of blood near the end of a clean glass microscope slide. Another slide is held at an angle, backed into the drop, and then smoothly dragged forward to spread the blood film along the slide. The blood must then be fixed, stained, and washed.

      When you view a properly prepared blood smear of a healthy individual, there are several populations of cells that you will notice. Keep in mind that these are all mature cells. The next section will discuss the identification of the immature cells of the bone marrow.

      • Erythrocytes, or red blood cells, are by far the predominant cell type in the blood smear. They are anucleate, non-granulated, eosinophilic cells that are uniform in shape (biconcave discs) and size (7.2 microns). Red blood cells have a central concavity that appears pale under the light microscope. These cells contain hemoglobin and are responsible for the transport and delivery of oxygen. Erythrocytes have a lifespan of 120 days.
      • Reticulocytes are immature red blood cells that are released from the bone marrow. They mature into erythrocytes after 1 to 2 days in the peripheral blood. There should be about one reticulocyte for every 100 red blood cells in a normal blood smear. These cells stain with a light blue tint because they still have RNA-containing organelles like free ribosomes.
      • Thrombocytes, or platelets, are the smallest elements of the blood and are responsible for the formation of clots through a complex, highly regulated cascade that you will study in Physiology and Immunobiology. Platelets are between 2 and 5 microns in diameter and appear ovoid and anucleate with purple granules.
      • Leukocytes, or white blood cells, are cells of the immune system that are present in both blood and interstitial fluid. There should be about 1 leukocyte for every 1000 red blood cells. They can be classified into two groups according to their nuclear pattern and the presence of cytoplasmic granules.

      Monomorphonuclear leukocytes are cells with round, non-lobed nuclei These include:

      • Small lymphocytes, which are about the same size as erythrocytes and have deeply stained nuclei with a thin rim of cytoplasm. This population includes both B-cells and T-cells.
      • Large lymphocytes, which appear similar to small lymphocytes, but with larger nuclei and a greater amount of cytoplasm. This population also includes both B-cells and T-cells. Lymphocyte counts are raised in response to viral infections.
      • Monocytes, which are larger than lymphocytes and have less-clearly demarcated nuclei that are usually not centered in the cell. These nuclei appear horseshoe-shaped and the cytoplasm contains fine granules that give it a muddy gray color. These granules contain lysosomal enzyme and peroxidase. Monocytes are phagocytic cells that are important in the inflammatory response. They are the precursors to the tissue macrophages that you studied in the Laboratory on Connective Tissue.

      Polymorphonuclear leukocytes are cells with lobed nuclei and cytoplasmic granules. While these cells share the same primary (nonspecific) or azurophilic granules, they are named based upon the characteristics of their secondary (specific) granules.

      • Neutrophils are by far the most numerous of the leukocytes. They are characterized by a nucleus that is segmented into three to five lobes that are joined by slender strands. The cytoplasm of neutrophils stains a pale pink. Its primary granules contain acid hydrolases and cationic proteins, and its secondary granules contain a variety of antimicrobial substances used to destroy bacteria that they phagocytose during the acute inflammatory response.
      • Eosinophils are larger than neutrophils and are distinguished by large red or orange granules of uniform size. These granules contain major basic protein, which is released to kill organisms too large to phagocytose, such as parasites and helminthes (worms).
      • Basophils are intermediate in size between neutrophils and eosinophils and have simple or bilobed nuclei. They contain many coarse purple granules that can vary in size or shape. These granules contain histamine, which is released to cause a vasoactive response in hypersensitivy reactions, and heparin, which is an anticoagulant. Basophils are not phagocytic.

      Component Cells of a Bone Marrow Smear

      While the peripheral blood smear indicates the status of mature blood cells, the bone marrow smear can be used to assess the process of hematopoiesis, or blood cell formation.

      Active bone marrow appears highly cellular. The majority of the developing cells will become erythrocytes, which confer a red color to the marrow. For this reason, active bone marrow is also known as red bone marrow. Over time, the marrow becomes less active and its fat content increases. It is then referred to as yellow bone marrow.

      Once again, there are several important characteristics to take into account when viewing a bone marrow smear. These include:

      • Size of the cell
      • Cytoplasm to nucleus volume ratio
      • Shape of the nucleus
      • Degree of chromatin condensation
      • Presence or absence of nucleoli
      • Cytoplasmic staining
      • Presence of cytoplasmic granules

      The blast cell is a pluripotent stem cell from which erythrocytes, granulocytes, and lymphocytes originate. Erythrocytes develop from erythryoblasts, granulocytes from myeloblasts, and lymphocytes from lymphoblasts. These cells, however, all appear identical - they are large with round or ovoid nuclei, a distinct nuclear membrane, visible nucleoli, and an abundant blue cytoplasm. As the blast cells differentiate, the resultant cells can be assigned to a particular cell line.

      Erythropoiesis is the development of red blood cells. There are several recognizable steps in this lineage:

      • The erythroblast develops into a proerythroblast, which is only slightly smaller than the blast, but has a more basophilic cytoplasm.
      • The basophilic erythroblast forms when the proerythroblast loses its nucleolus. These cells are much smaller than the blast cells and have an intensely basophilic cytoplasm that results from the accumulation of ribosomes.
      • The polychromatophilic erythroblast has a darkly staining nucleus and its cytoplasm stains a grayish-green color due to the accumulation of hemoglobin.
      • In the orthochromatic erythroblast, or normoblast, the nucleus becomes smaller and darker and the cytoplasm becomes pinker. Nuclear expulsion occurs at the end of this stage through an asymmetric division of the orthochromatic erythroblast. The portion that contains the cytoplasm and organelles becomes the reticulocyte, while the portion containing the nucleus is destroyed by macrophages.
      • The reticulocyte contains cytoplasm, cytoplasmic organelles, and many ribosomes. It is released from the bone marrow and develops into a mature erythrocyte after spending 1 to 2 days in the peripheral blood.

      Granulopoiesis is the process by which white blood cells develop. The myeloid series has the most characteristic cell lineage:

      • The myeloblast differentiates into a promyelocyte that becomes irreversibly committed to the neutrophilic cell line. This cell is large, with a large round nucleus, prominent nucleoli, and purple azurophilic granules. These granules are primary, nonspecific granules. Promyelocytes also give rise to eosinophils and basophils
      • The myelocyte stage is characterized by the production of secondary, specific granules. Myelocytes can vary in cell size and nuclear shape. They contain both the purple staining azurophilic granules and lilac staining specific granules. As they develop, they decrease in size, their nucleus becomes indented, and there is a shift toward more specific granules. There is also a reduction in the number of organelles, which results in decreased basophilia of the cytoplasm.
      • The metamyelocyte has a flattened nucleus with condense chromatin.
      • The band cell has a horseshoe-shaped nucleus that is "immature." As development continues, it will mature into a segmented nucleus with multiple lobes. It will then be a mature neutrophil.

      Eosinophils and basophils undergo sequential stages of differentiation in a very similar manner to those of neutrophils. Their specific granules are also produced during the myelocyte stage.

      The platelet lineage is similar. Large, multilobed promegakaryocytes develop into megakaryocytes, which are the largest cells of the bone marrow (30 to 40 microns). Platelets form through the segmentation of these cells.

      Monocytes develop from promonocytes and lymphocytes develop from prolymphocytes. These elements are difficult to distinguish in normal bone marrow smears.

      28 Aug 2015: The PLOS ONE Staff (2015) Correction: The Gametocytes of Leucocytozoon sabrazesi Infect Chicken Thrombocytes, Not Other Blood Cells. PLOS ONE 10(8): e0137490. View correction

      Leucocytozoon parasites infect a large number of avian hosts, including domestic chicken, and cause significant economical loss to the poultry industry. Although the transmission stages of the parasites were observed in avian blood cells more than a century ago, the specific host cell type(s) that the gametocytes infect remain uncertain. Because all the avian blood cells, including red blood cells (RBCs), are nucleated, and the developing parasites dramatically change the morphology of the infected host cells, it has been difficult to identify Leucocytozoon infected host cell(s). Here we use cell-type specific antibodies to investigate the identities of the host cells infected by Leucocytozoon sabrazesi gametocytes. Anti-RBC antibodies stained RBCs membrane strongly, but not the parasite-infected cells, ruling out the possibility of RBCs being the infected host cells. Antibodies recognizing various leukocytes including heterophils, monocytes, lymphocytes, and macrophages did not stain the infected cells either. Antisera raised against a peptide of the parasite cytochrome B (CYTB) stained parasite-infected cells and some leukocytes, particularly cells with a single round nucleus as well as clear/pale cytoplasm suggestive of thrombocytes. Finally, a monoclonal antibody known to specifically bind chicken thrombocytes also stained the infected cells, confirming that L. sabrazesi gametocytes develop within chicken thrombocytes. The identification of L. sabrazesi infected host cell solves a long unresolved puzzle and provides important information for studying parasite invasion of host cells and for developing reagents to interrupt parasite transmission.

      Citation: Zhao W, Liu J, Xu R, Zhang C, Pang Q, Chen X, et al. (2015) The Gametocytes of Leucocytozoon sabrazesi Infect Chicken Thrombocytes, Not Other Blood Cells. PLoS ONE 10(7): e0133478.

      Editor: Richard Culleton, Institute of Tropical Medicine, JAPAN

      Received: May 8, 2015 Accepted: June 28, 2015 Published: July 28, 2015

      This is an open access article, free of all copyright, and may be freely reproduced, distributed, transmitted, modified, built upon, or otherwise used by anyone for any lawful purpose. The work is made available under the Creative Commons CC0 public domain dedication

      Data Availability: All relevant data are within the paper.

      Funding: This work was supported by the National Natural Science Foundation of China #81220108019, 81271858, and #81201324, by Project 111 of the State Bureau of Foreign Experts and Ministry of Education of China (B06016), and by the Division of Intramural Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

      Competing interests: The authors have declared that no competing interests exist.

      Examining a Mammalian Blood Smear

      Obviously we must use extreme caution when handling human blood or blood products because of the risk of transmission of the human immunodeficiency virus (HIV). Unfortunately, the use of human blood in teaching labs is no longer practical, although the concerns are more about liability and insurance rather than actual risk (love those lawyers!). As far as we know, animal blood poses no risk from HIV, and very few blood diseases are transmissible from animals to humans. Laboratory bred animals in particular pose essentially no risk at all.

      Examinations should be made of freshly collected blood samples. Whole human or animal blood that has been treated with an anticoagulant can be maintained under refrigeration for an extended period of time and remain of use for research or for clinical applications. However, after a few hours, the white blood cells begin to clump and to deteriorate. Some information can be obtained after a day or two, but such smears are usually disappointing compared to those of fresh blood.

      Microscopic examination of whole blood begins with the preparation of a smear. A small drop of blood is placed at one end of a very clean glass slide, and the edge of a second slide is drawn across the drop at an angle so that capillary action spreads the drop along the edge. The second slide is then pushed in one smooth motion to the opposite end of the first slide, spreading the drop across the slide to make the smear.

      After the smear has dried it can be stained by applying a liberal amount of Wright's stain with a pasteur pipet. Wright's stain contains red and blue dyes that are acidophilic ('acid-loving') and basophilic ('alkaline-loving'), respectively. Avoid skin contact, since most stains are toxic. The stain is allowed to remain on the slide for about 2 minutes, and more is added if it begins to dry up. After a short dip in buffer and/or a rinse in deionized water, the smear is gently blotted dry with bibulous (absorbant) paper. Incidentally, many students have a problem with common sense - my apologies if this insults your intelligence, but DO remove the sheet of bibulous paper from the book before using it for blotting. Don't simply blot the slide onto the entire book.

      Microscopic examination of formed elements

      Because mammalian red blood cells are biconcave they will not appear as uniform disks in the microscope field. Examination at 400x reveals them to be thin in the center. All of the formed elements should be examined at 1000x using the oil immersion technique in order to make positive identifications and to see the fine detail. The drop of oil should be placed directly on the smear.

      Most leukocytes (white blood cells) are larger than the erythrocytes, and unless the donor had a nasty blood disease, they will be much more scarce. The two major categories of leukocytes are the granulocytes and the agranulocytes, based on the presence of visible cytoplasmic granules in one type and the absence of visible granules in the other. Each major type is further composed of recognizable sub-types based on staining properties of the granules, size of cell, and proportion of nuclear to cytoplasmic material.


      The sex of a blood donor can be determined by examining the neutrophils. Human males have only one copy of the X-chromosome, the genes of which are expressed. In human females, only one X-chromosome in each cell is expressed, while the second is condensed, making the alleles it carries inaccessible. The condensed X-chromosome may jut out as a very small but obvious 'lobe' of the nucleus of the neutrophils, called a Barr body.

      Basophils and eosinophils are granulocytes with cytoplasmic granules that stain with basophilic (blue) and acidophilic (red) dyes respectively. Wright-stained basophils are spectacular in appearance, and are usually the rarest of leukocytes. Their granules appear quite large and they stain nearly black, often obscuring the nucleus. The eosinophils, which are often present in large numbers in the presence of a parasitic infection, have numerous red-staining granules.



      The stem cells from which red cells and leukocytes are developed are found in the bone marrow. Also in the bone marrow are giant cells called megakaryocytes. Megakaryocytes disintegrate before enter the bloodstream, so that only the fragments, called platelets, remain. When platelets encounter a damaged surface they swell and stick to the surface and each other to form a plug. The plug seals blood vessels, allowing time for the slower clotting process to take place and form a tight seal. Platelets have no pigmentation, and only lightly stain with Wright's stain, so you may need phase contrast to see them.


      1. The complete blood count (CBC) is a laboratory test that, among other things, determines the total number of both leukocytes and erythrocytes per ml of blood.
      2. In general, an elevated WBC count (leukocytosis ) is seen in infection, inflammation, leukemia, and parasitic infestations.
      3. Neutrophils are the most abundant of the leukocytes, normally accounting for 54-75% of the WBCs. Neutrophils are important phagocytes and also promote inflammation.
      4. Eosinophils normally comprise 1-4% of the WBCs. They are capable of phagocytosis but primarily they release their contents into the surrounding environment to kill microbes, especially parasitic worms, extracellularly. They also promote inflammation.
      5. Basophils normally make up 0-1% of the WBCs and release histamine, leukotrienes, and prostaglandins, chemicals that promotes inflammation.
      6. Monocytes normally make up 2-8% of the WBCs and differentiate into macrophages and dendritic cells when they leave the blood and enter the tissue.
      7. Lymphocytes normally represent 25-40% of the WBCs and mediate the specific immune responses.
      8. B-lymphocytes (B-cells) mediate humoral immunity, the production of antibody molecules against a specific antigen, and have B-cell receptors (BCR) on their surface for antigen recognition. Most B-lymphocytes differentiate into antibody-secreting plasma cells.
      9. T-lymphocytes (T-cells) are responsible for cell-mediated immunity, the production of cytotoxic T-lymphocytes (CTLs), activated macrophages, activated NK cells, and cytokines against a specific antigen.
      10. T4-lymphocytes have CD4 molecules and T-cell receptors on their surface for antigen recognition. They function to regulate the adaptive immune responses through cytokine production. Once activated, they differentiate into effector T4-lymphocytes.
      11. T8-lymphocytes have CD8 molecules and T-cell receptors on their surface for antigen recognition. Once activated, they differentiate into T8-suppressor cells and cytotoxic T-lymphocytes (CTLs).
      12. NK cells (natural killer cells) are lymphocytes that lack B-cell receptors and T-cell receptors. They function to kill infected cells and tumor cells.

      Watch the video: What Are White Blood Cells. Health. Biology. FuseSchool (February 2023).