[Significance of the immune complex reaction in internal medicine].

A review is given concerning occurrence, identification, and pathogenetic effects of immune complexes. The formation of immune complexes by interaction of antigen with antibody, is a component of the normal immune response. In cases with inefficient clearance by the mononuclear phagocyte system only, pathological consequences will be expected, in particular by immune complexes formed with moderate excess of antigen. For the identification of immune complexes in biological fluids many methods have been developed. The methods are based mostly on biological activities of immune complexes, e.g. interaction with complement or rheumatoid factor and reactivity with cellular receptors. These antigen-nonspecific methods do not allow to discriminate between true immune complexes and nonspecifically aggregated immunoglobulins. Circulating immune complexes become fixed to basement membranes of the body. They can produce an acute inflammatory reaction by activation of complement and inflammatory cells and also interfere with the immune response. Circulating immune complexes have been detected in some human diseases, e.g. autoimmune diseases (LEV, RA), infectious diseases, malignancies, serum sickness syndrome, immune-complex glomerulonephritis, and after transplantation. The possibilities for management of immune complex diseases are discussed.