Failure to find C1q-binding material and anti-IgG antibodies in ankylosing spondylitis

C1q-binding immune complexes (C1C), anti-IgG antibodies (anti-IgG Ab), and complement levels were investigated in the serum of 37 patients with ankylosing spondylitis (AS). In all these studies the mean levels observed in patients with AS were similar to those in 31 normal subjects. Moreover, no significative difference in either CIC or anti-IgG Ab levels was observed when the patients were classified in different clinical forms according to the localisation (peripheral and central) or to the gravity (mild and severe) of the AS. In a parallel study increased CIC and anti-IgG Ab levels were found in most of the 81 patients with seropositive or seronegative rheumatoid arthritis.