Immunological Response against Allogeneic Chondrocytes Transplanted into Joint Surface Defects in Rats

Rat chondrocytes isolated from the articular–epiphyseal cartilage complex were transplanted into defects prepared in articular cartilage and subchondral bone. Transplants were taken for examination after 3 and 8 wk. Cartilage formed by syngeneic chondrocytes did not evoke formation of infiltrations. Contrary to that, in the vicinity of cartilage produced by allogeneic chondrocytes numerous infiltrating cells were present and cartilage resorption could be observed. Cyclosporine-A (CsA) treatment of recipients of allogeneic chondrocytes only partially suppressed accumulation of infiltrating cells and matrix resorption. Antichondrocyte immune response of chondrocyte graft recipients was studied by evaluation of spleen mononuclear cells (SMC) stimulation in mixed splenocytechondrocyte cultures and by evaluation of antichondrocyte cytotoxic antibodies. No difference in stimulation of SMC from intact rats by syngeneic and allogeneic chondrocytes was observed. Stimulation by allogeneic chondrocytes was slightly but significantly higher in recipients of syngeneic grafts. SMC of allogenic chondrocyte recipients were strongly stimulated by allogeneic chondrocytes. This response was absent in recipients treated with CsA. Spontaneous antichondrocyte cytotoxic antibody activity was detected in intact rats and in recipients of syngeneic grafts. In recipients of allogeneic chondrocytes the antibody response against allogeneic chondrocytes was raised but was statistically not significant owing to the considerable variation in the level of spontaneously occurring antichondrocyte antibodies.