Circulating immune complexes (CIC) - complexes consisting of antigens, antibodies and associated components of complement C3, C4, C1q. Normally, immune complexes formed in the bloodstream are phagocytosed and destroyed. With an increase in their size (with an excess of antigens and the presence in the structure of IgM, the complement component of C1q), complexes can be deposited in the perivascular space and the cortical layer of the kidneys, causing complement activation and inflammatory processes.
