Suppressive effects of anti-mu serum on the development of collagen arthritis in rats

Sprague-Dawley rats were maintained in environmentally isolated conditions and some of them were injected beginning at birth with rabbit anti-mu serum to suppress B-cell maturation. All rats were subsequently immunized with chick type II collagen. Ten (28%) of 36 rats injected with anti-mu antiserum failed to develop serum hemagglutinating antibodies to collagen, and there was a significant (P less than 0.0003) reduction in the IgG-specific antibody titer to collagen in these 10 rats compared to the other 26 rats in this group. Only 1 (10%) of the antibody-suppressed rats developed arthritis compared to 20 (77%) of the 26 other rats in the anti-mu-treated group (P less than 0.001). Twenty-two (61%) of 36 immunized rats administered rabbit anti-ovalbumin serum and 14 (88%) of 16 immunized rats kept in the axenic conditions developed arthritis. Delayed-type hypersensitivity to collagen did not differ significantly between the groups. These data provide indirect evidence that antibodies play a role in the inception of collagen arthritis.