13.1 Leucocyte system
13.2 Physiological system of immune response
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13.1. Leucocyte system
The leukocyte system is a physiological system consisting of circulating WBCs, organs of their formation and destruction, united in a single system by the apparatus of neurohumoral regulation. Leukocyte formation
Places of leukopoiesis in the body: myeloid tissue of the bone marrow (formation of granulocytes, mono-cytes, B lymphocytes and T lymphocyte precursors) and lymphoid tissue (differentiation and reproduction of B and T lymphocytes, plasmocytes). Leukopoiesis scheme.
Granulocytopoiesis: HSC → polypotent precursor (CFU-GEMM) → bipotent preceptors (CFUneut. eos.; CFUgr.mon.; CFUgr.er.) → unipotent precursors (CFUneut.; CFUbas.; CFUeos.) → corresponding myeloblasts → promyelocytes → myelocytes → metamyelocytes → band neutrophils → segmented neutrophils (neutrophils, eosinophils, basophils).
Monocytopoiesis: HSC → polypotent precursor (CFU-GEMM) → bipotent preceptor (CFUgr.mon.) → unipotent precursor (CFUmon.) → monoblast → promonocyte → monocyte.
Lymphopoiesis: HSC → polypotent precursor of lymphopoiesis (CFUlymph.) → precursor of Т and В lymphocytes (pre-CFU-Т, preCFUВ) → Т and В lym-phoblasts → Т and В lymphocytes (Fig. 13.1).
Leukocytes of circulating blood
Quantitative characteristic. The number of WBCs in the blood is 4-9×109/l.
Types and functions of leukocytes. The percentage of different types of granulocytes and agranulocytes comprise the WBC formula.
Neutrophils (48-78% of the total WBC number).
The main function of neutrophils is phagocytosis and destruction of microbes and cellular debris. It is provided by the following properties. Neutrophils form exogenous chemotaxis factors: granulocyte and monocyte CSF, IL-6 (or interferon β2) and others, which attract neutrophils to the object of phagocytosis. On the plasmolemma there are receptors for immunoglobulins, complement proteins, adhesion molecules, by which the objects of phagocytosis are attached to neutrophils. The latter form pseudopodia that surround phagocytosed bodies with formation of phagosomes.