Quantitation of complement proteins in rheumatic disease.

Complement proteins serve a critical function in the non-antigen-specific elimination of foreign substances and organisms and of immune complexes. Studies of genetic and acquired alterations of complement proteins have provided insights into the pathophysiology of a number of rheumatic diseases, especially those in which immune complexes are believed to have a role in pathogenesis. Complement levels may be helpful in the management of some patients with SLE or vasculitis, and in evaluation of synovial, pleural and pericardial fluids.