Leukocyte Formation, Types, and Function 2020 PDF

By Abdulfatah albakkosh INTRODUCTION • The leukocyte develop from pluripotential stem cell in the bone marrow. • under the influence of hematopiotic growth factors, the stem cell matures into terminally differentiated cells. • These cells circulate only for a few hours in the peripheral blood bef...

By Abdulfatah albakkosh INTRODUCTION • The leukocyte develop from pluripotential stem cell in the bone marrow. • under the influence of hematopiotic growth factors, the stem cell matures into terminally differentiated cells. • These cells circulate only for a few hours in the peripheral blood before migrating to the tissues. • The leukocytes serve as the defenders of the body against foreign invaders. • They are attracted to the site of inflammation, infection, or tissue injury by chemoattractants. Hematopoiesis Hematopoietic cells during differentiation • Stem cells: • Rare cells, proliferate at low level, self-renew • Pluripotential stem cell • Lymphoid multipotential cell, Myeloid multipotential cell • Progenitor Cells • Source of differentiated cells, influenced by growth factors, reduced multipotentiality • Colony forming cells ( or units, CFC or CFU), • eg. CFU-E: erythrocyte-colony forming cell or unit • Precursor Cells (blasts) • High mitotic activity, lineage committed • e.g Lymphoblast, erythroblast etc. • Mature cells • No mitotic activity, abundant in peripheral blood 5 MYELOPOIESIS Schematic illustration of granulocytic cell differentiation Myeloblast Immature Precursor No granules Promyelocyte • • No granules Slightly larger cell Primary granules Myelocytes • Coarser chromatin • Nucleoli not seen • Secondary granules Band form • Nucleus lobated Neutrophil • Lobes separated by narrow structure Metamyelocyte • Indented nucleus Five types of Human Leukocytes • The five types of WBCs 1. 2. 3. 4. 5. Neutrophils Lymphocytes Monocytes Eosinophils Basophils Total leukocyte count: 4.000 -11.000/mm3 in adult - Number of WBCs is less than RBCs count because it has short life span. 8 1- POLYMORPHONUCEAR NEUTROPHIL:(PMN) • Neutrophils constitute the majority of circulatory leukocytes (40-60%). • as indicated by its name, it has a segmented nucleus with two to four lobes that are joined by a thin nuclear filament. • The chromatin has condensed and stained black-purple. • The mature PMN cytoplasm includes many secondary granules and is stained pink. • Neutrophils have an average lifespan of 10 hours before moving to tissues through the blood vessel wall. FUNCTION OF NEUTROPHIL • Neutrophils exit blood vessels and travel to sites of tissue injury or infection. • migration is facilitated by chemoattractant molecules ( like complement, leukotrins, and products from viruses and bacteria). • Once in the inflamed region, the neutrophil must identify the particle as foreign before attachment and phagocytosis can proceed. • After the particle is found and attached, the neutrophil's pseudopods wrap around it to make a phagosome. • The granules of neutrophil fuse with the digesting phagosome to produce a phagolysosome. • The microorganism-killing enzyme of the granules is exocytosed along with the contents. 2-EOSINOPHILS: • Eosinophils have a concentration in peripheral blood from 1-3%. • They spend very little time in the peripheral blood( 1-8 hours) before migration to the tissues. • the nucleus of mature eosinophil has no more than two or three lobes. • The cytoplasm is filled with red –orange granules. • Eosinophils are associated with allergic reactions, parasite infection and chronic inflammation. 3-BASOPHILS: • its constitute from 0-1% of the total leukocyte • they have bilobed nucleous and large purple- black granules distributed throughout the cytoplasm. -The granules contain histamine and heparin. -its function as mediators of inflammatory responses especially those of hypersensitivity and allergic reactions. Basophils 1. < 1% of leukocytes 2. 12-15 mm diam. 3. 0.5 mm diam.basophilic granules 4-MONOCYTE: • The monocyte is largest cells in the peripheral blood. • The nucleous is irregular, frequently horseshoe or bean like. • The cytoplasm has a blue-gray color with dust-like particles. • The monocyte leave the blood and enters the tissues, where it matures into a macrophage. • The normal range of monocyte between 2-8%. • The monocyte and macrophage function as phagocytes ( ingest and kill microorganism), 5-LYMPHOCYTE: • The lymphocyte generally classified as large and mature lymphocyte. • The nucleus is about the size of erythrocyte and occupies about 90% of the cell area. • The chromatin is deeply condensed and dark purple in color. • The nucleus is surrounded by a small amount of sky-blue cytoplasm and few azurophilic granules and vacuoles may be present. • Two types of lymphocyte( T, B lymphocyte) • The lymphocyte account between 20-40% function of lymphocyte • The T lymphocyte responsible cell mediated immunity • The B lymphocyte responsible for humeral immunity( production of antibodies). Aisha NASEF Remember that No.,count, types ,and even function of WBC , can be obtained from CBC, DLC ,and PBF Aisha NASEF Normal WBC count mild increase High count Aisha NASEF