Enzymatic alteration of C1q, the collagen-like subcomponent of the first component of complement, leads to cross-reactivity with type II collagen

AbstractNative serum C1q, the collagenous-like subcomponent of the first component of complement, is not recognized by polyclonal anti-collagen type II antibodies. However, when purified C1q was subjected to limited proteolysis by collagenase it showed antigenic cross-reactivity with collagen type II. The same cross-reactivity was observed with hemolytically active C1q in synovial fluids of patients with rheumatoid arthritis (RA), whereas C1q from synovial fluids of patients with osteoarthritis (OA), villo-nodular synovitis and ankylosing spondylitis was not recognized by this antibody. However, incubation of synovial fluid C1q of OA patients with synovial fluid leucocytes from RA patients …