Physicochemical and functional relationships of immune complexes.

The biological properties of immune complexes depend on the nature of antigens and antibodies comprising these complexes. The lattice of immune complexes influences their tissue deposition, complement activation, and interaction with Fc receptors. The lattice of immune complexes depends on the valence of antigens, the antigen-antibody ratio, the association constant of these reactants and the concentration of antigen and antibody. Kupffer cells effectively remove large-latticed immune complexes from the circulation due to their Fc receptors. This system is saturable, leading to prolonged circulation of the complexes and enhanced deposition in tissues. Small-latticed immune complexes are slowly removed from the circulation by yet unidentified mechanisms. The renal glomerulus serves as an example of immune complex deposition from the circulation. Only large-latticed complexes are deposited in the glomerular capillary wall in the subendothelial area and the mesangial matrix. An influx of bone marrow-derived monocytes participates in the disposal of immune complexes deposited in these areas of the glomerulus, the resident mesangial cells do not phagocytize these substances. The subepithelial deposits of immune complexes appear to be locally formed and not deposited from the circulation.