[The nature of macrophage functional heterogeneity exemplified by Fc receptors]

It is known that functional activity of macrophages (Mph), adhesion and phagocytosis, depends on the local concentration of Fc receptors (Fc gamma R) on the cell surface. Fc gamma R may have a random distribution on cell membrane or form clusters of different sizes. This process depends on the local activity of microfilaments that, in its turn, reflects peculiarities of macrophage microenvironments. One may conceive that the number of opsonized erythrocytes (OE) subject to adhesion (engulfing) to separate Mph depends on the amount of active centres on the cell surface and their activity. The structures, such as Fc gamma R clusters, phagosomes and others, in whose formation numerous components of Mph (cell skeleton, microvesicles, signal receptive system and others) are involved, are arbitrarily called the structural functional units (SFU). Thus, we used two parameters: the average number of SFU per Mph in population, and the average activity of SFU instead of a generally accepted number of OE per Mph. The number of SFU per Mph can be 0, 1, 2 etc., and one SFU may bind (engulf) 0, 1, 2 etc. EA. For the assessment of the parameters, the approximation of experimental histograms by type-A Neyman's distribution was used. To verify the adequacy of the model, observations of OE adhesion and phagocytosis in different conditions were made. The results show that the parameters of the model fit well the biological processes in this system.