FORMATION OF WHITE BLOOD CELLS Dr. B.L. Mtinangi. Department of Physiology School of Medicine, MUHAS November, 2015

FORMATION OF WBC As for the Rbc, the formation of Wbc originates from the COMMON PROGENITOR CELL ie uncognisable cell which develop to the UNCOMMITTED STERM CELL and this changes to COMMITTED STERM CELL

FORMATION OF WBC CONT. Committed sterm cell can either develop into: Myeloblast series or Monoblast or Lymphoblast series. Myeloblast changes into Promyelocyte & the Promyelocyte to Myelocyte which will either develop into NEUTROPHIL or BASOPHIL or EOSINOPHIL.

FORMATION OF WBC CONT. Monoblast develop into: Monocyte in the circulating blood Tissue Macrophage ie the Monocyte that has moved into various tissues. Lymphoblast from Lymphogenous organs develop into Prolymphocyte which will then develop into: Large Lymphocyte & Small Lymphocyte

WBC CONT. White blood cells are Leucocytes & Macrophages that are involved in the defence mechanisms against: Bacteria Viruses Fungus & Parasites

WBC CONT. Mechanism of action of Wbc is either Phagocytic eg neutrophil, eosinophil, basophil & monocytes OR Antibodies formation eg lymphocytes Wbc are of two types: With granules (Granulocytes) Without granules (Agranulocytes) Normal Wbc count ranges from 4000 to 11000/micro litre

WBC CONT. Wbc with granules (granulocytes) are Neutrophils 40 – 70% (60%) Eosinophil 1 – 4% (3%) Basophil 0 - 2% (1%) Wbc without granules (agranulocytes) Lymphocytes 20 – 45% (30%) Monocytes 4 - 8% (6%) NB. Platelets are sometimes grouped as Wbc

FUNCTIONS OF WBC Granulocytes and Monocytes are for PHAGOCYTOSIS Lymphocytes are for IMMUNITY ie Cell mediated immunity & Antibody formation Platelets are for blood clotting (COAGULATION) mechanisms

Type Of White Blood Cells Lymphocytes (B Cells and T Cells) % By Volume Of WBC Description Function Neutrophils 60 – 70 % Nucleus has many interconnected lobes; blue granules Phagocytize and destory bacteria; most numerous WBC Eosinophils 2 – 4 % Nucleus has bilobed nuclei; red or yellow granules containing digestive enzymes Play a role in ending allergic reactions Basophils < 1 % Bilobed nuclei hidden by large purple granules full of chemical mediators of inflammation Function in inflammation medication; similar in function to mast cells Lymphocytes (B Cells and T Cells) 20 – 25 % Dense, purple staining, round nucleus; little cytoplasm the most important cells of the immune system; effective in fighting infectious organisms; act against a specific foreign molecule (antigen) Monocytes 4 – 8 % Largest leukocyte; kidney shaped nucleus Transform into macrophages; phagocytic cells

WBC CHARACTERISTICS Each Wbc has specific distinguishing characteristics in terms of: Cell size The shape of Nuclear Cytoplasmic content Type of granules & Phagocytic activity of the cell

LIFE SPAN OF WBC The life span of the Wbc differs depending on the type of Wbc: Granulocytes have a life span of 4 to 8 hrs in the circulation and 4 to 5 days in tissues Monocytes have a short transit in circulation then go to TISSUES as Tissue macrophages Lymphocytes have a life span of about 100 to 300 days, tend to recirculate. Some are known to have a life span of 7 years

MECHANISM OF CELL PHAGOCYTOSIS Margination ie lining of cells(Wbc) on the capillaries due to bacteria products or toxins Diapedesis ie squeezing through small pores in blood capillaries Migration ie ameboid or psedopodia motion esp Neutrophils & macrophages Chemotaxis ie movements due to bacteria toxins & inflammation. All cause a directional migration of NEUTROPHIL & MACROPHAGES to the site of injury or infection

PHAGOCYTOSIS CONT. The process of phagocytosis: Bacteria are ENGULFED by Pseudopodia & Fusion Bacteria then lies within a cel l vacuole with phagosome Lysosomal or digestive enzymes are secreted into phagosome causing Degranulation & Lysis of the bacteria leading to DEATH

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