Immunological changes in canine cruciate ligament rupture.

Samples of sera (39) and synovial fluid (36) from 58 dogs suffering from inflammatory arthropathy of the stifle joints, 47 of them in combination with unilateral or bilateral rupture of the anterior cruciate ligaments (CLR), were investigated for C1q-binding immune complexes (IC) using a solid phase radioimmunoassay. In 31 out of 39 sera (79 per cent) and 25 out of 36 synovial fluids (69 per cent) significant IC concentrations could be detected. As controls 21 healthy dogs were used. The radioimmunoassay was standardised with aggregated dog gamma globulin. The sera of the dogs were also investigated for anticollagen antibodies to denaturated type 1 or type 2 dog collagens. No evidence of the presence of these antibodies could be obtained. In a small percentage of sera and, or, synovial fluids rheumatoid factor could be demonstrated. These results indicate that the CLR in dogs is accompanied by immunological mechanisms.