Serum IgA1 and IgA2 subclass antibodies against collagens in patients with ankylosing spondylitis.

We measured IgA1 and IgA2 subclass antibody levels against human type I, II, III and IV collagens in patients with ankylosing spondylitis (AS) by enzyme linked immunosorbent assay (ELISA). Significant elevations of IgA1 antibodies against type II collagen (p<0.01) and IgA2 antibodies against type I (p<0.001), III (p<0.001), and IV (p<0.01) collagens were observed in AS patients compared with those of healthy controls. These findings suggest that serum IgA antibodies against type I, III and IV collagens were mainly produced in secretory lesions in AS patients.