ANTIBODIES TO TYPE-II COLLAGEN IN HUMAN SERUM - STORAGE EFFECTS AND ROLE OF IGM ANTIIDIOTYPE IN REGULATION

Objective. To investigate the observation that IgG reactivity to human denatured type II collagen (denatured CII) is increased in normal hum an serum stored at 4 degrees C compared to serum stored at -20 degrees C. Methods. Reactivity was measured by ELISA, and the effect of heati ng was also assessed. Serum was separated on affinity columns and mixi ng experiments were performed with the resultant fractions to test for inhibitory or enhancing effects. Results. There is a storage labile a nd heat labile inhibitor in the IgG depleted fraction of serum stored at -20 degrees C from healthy subjects, and an inhibitor is present in some pooled human IgM preparations which reduces the reactivity of an tibody to human CII in serum from both healthy subjects and patients w ith rheumatoid arthritis. Conclusions. Storage conditions and heat sig nificantly affect IgG antibodies to denatured CII but not antibodies t o other antigens. These effects may be mediated by the presence of an IgM antiidiotype against the IgG antibody to denatured CII.