Collagen-induced acute synovitis in collagen-immunized rabbits.

Thirty rabbits were investigated in 3 groups: a) one consisting of non-immunized animsls which were injected intraarticularly with human soluble collagen, human gammaglobulin or saline, b) the other consisting of human gammaglobulin-immunized animals which were injected with human soluble collagen and human gammaglobulin into the knee joints, and c) the third consisting of human collagen-immunized rabbits which were injected with human soluble collagen and human gammaglobulin into the knee joints. Eighteen hours after injection animals were sacrificed, joint fluid collected, cell number in fluid determined and synovial tissue prepared for histologic investigation. Distinct acute synovitis was observed in collagen injected knees of collagen immunized rabbits, as shown by distinctly increased cell number in fluids and histologic investigation. In comparison to collagen- or gammaglobulin injected knees of non-immunized animals, increase in cell number of collagen injected knees of collagen injected animals was statistically significant with P less than 0.005 respectively with P less than 0.01, and with P less than 0.025 in comparison to gammaglobulin injected contralateral knee. Distinct acute inflammation was observed morphologically in synovial tissue of collagen injected knees of collagen immunized animals only. Acute synovitis was also observed in positive controls, i.e. gammaglobulin injected knees of gammaglobulin immunized animals. These observations show, that appearance of collagen in molecular disposable form can induce acute inflammation of joints in state of collagen immunization.