White Blood Cells PDF - Types and Functions

WHITE BLOOD CELLS  Introduction ▪ There are five types of white blood cells; these are divided into two main classes: ✓ GRANULOCYTES - includes neutrophils, eosinophils and basophils; ✓ AGRANULOCYTES - includes lymphocytes and monocytes  Neutrophils...

WHITE BLOOD CELLS  Introduction ▪ There are five types of white blood cells; these are divided into two main classes: ✓ GRANULOCYTES - includes neutrophils, eosinophils and basophils; ✓ AGRANULOCYTES - includes lymphocytes and monocytes  Neutrophils ▪ Neutrophils are the commonest type of WBC found in a blood smear; they make up 60-70% of the total amount of WBCs. ▪ They are 12-14 µm diameter. ▪ There is a single nucleus, which is multilobed, and can have between 2 and 5 lobes. ▪ The chromatin in the nucleus is condensed; Neutrophil there are few organelles in the cytoplasm. ▪ Neutrophils have 3 types of granules: 1. azure granules (lysosomes), 2. secretory granules in salmon pink cytoplasm, anti- microbial enzymes. 3. have glycoproteins and gelatinase. ▪ Neutrophils are produced in the bone marrow; they circulate in the blood for 6-10 hours, and then enter the tissues. ▪ They are motile, and phagocytic and will destroy damaged tissue and bacteria. ▪ They are important in inflammatory reactions.  Eosinophils ▪ Eosinophils make up 1-6% of the total WBCs. ▪ These cells are 12 - 17 µm in diameter. ▪ Eosinophils only have two lobes to their nucleus. ▪ These cells have large acidophilic specific granules - these stain bright red, or reddish- purple. ▪ These granules contain proteins that are 'destructive' and toxic. Eosinophil ▪ They are produced in the bone marrow, and migrate from the peripheral blood system after a few hours, into loose connective tissue in the respiratory and gastrointestinal tracts. ▪ They phagocytose antigen-antibody complexes. ▪ They also produce histaminase, and aryl sulphatase B, two enzymes that inactivate two inflammatory agents released by mast cells. ▪ A high eosinophil blood count may indicate an allergic reaction. ▪ Eosinophils are also important in killing parasitic worms.  Basophils ▪ Basophils make up only 1% of the WBCs found in a blood smear. ▪ They are 14-16 µm in diameter, contain lots of deep blue staining granules and a bilobed nucleus. ▪ The granules contain heparin, histamine and serotonin. prostaglandins and leukotrienes. Basophil ▪ These cells are involved in immune responses to parasites. ▪ They have IgE receptors and the granules are released when the cells bind IgE. ▪ These cells also accumulate at sites of infection, and the release of prostaglandins, serotonin and histamine help to increase blood flow to the area of damage, as part of the inflammatory response. ▪ The degranulation - release of histamine also plays a role in allergic reactions such as hay fever.  Lymphocytes ▪ Small lymphocytes measure about 6-9µm, whereas large lymphocytes are about 10-14µm in size. ▪ Small lymphocytes have a small spherical nucleus Small lymphocyte and have abundant dark staining condensed chromatin. ▪ Not much cytoplasm can be seen, and it is basophilic. ▪ Lymphocytes make up 20-50% of the WBCs found Large lymphocyte in a blood smear. ▪ There are two main types of lymphocytes; B-cells and T-cells. Large granular lymphocyte ▪ B-cells develop in the bone marrow; T cells are produced in the bone marrow, but are matured in the thymus. ▪ The B-cells develop into plasma cells which make antibodies. ▪ The T-cells attack viruses, cancer cells, and transplants. Plasma cell ▪ The larger lymphocytes have more cytoplasm, more free ribosomes and mitochondria. ▪ Larger lymphocytes are commonly activated lymphocytes.  Monocytes ▪ Monocytes are the largest type of WBCs, and can be up to 20µm in diameter. ▪ They have a large eccentrically placed nucleus, which is kidney bean shaped. ▪ They have abundant cytoplasm, and some fine pink/purple granules in cytoplasm. ▪ Monocytes make up about 2-10% of Typical monocyte. Note the vacuolated cytoplasm, a contorted nucleus that folds on itself, loose or lacelike chromatin pattern, and very fine azure leucocytes. granules ▪ Monocytes circulate in the blood for 1-3 days, and then migrate into body tissues, where they transform into macrophages. ▪ They will phagocytose dead cells and bacteria. ▪ Some monocytes can also transform into osteoclasts. ▪ Monocytes are important in the inflammatory response. END