Cartilage produced after transplantation of syngeneic chondrocytes is rejected in rats presensitized with allogeneic chondrocytes

Cartilage produced in 2-week-old intramuscular transplants of syngeneic cho ndrocytes in rats did not display any signs of rejection. Cartilage produce d by similar transplants in animals presensitized with intramuscular transp lants of allogeneic chondrocytes was surrounded by infiltrations composed m ainly of lymphocytes and was partially resorbed. Spleen mononuclear cells ( SMC) from recipients of syngeneic transplants alone were not stimulated in mixed splenocyte-chondrocyte cultures by syngeneic or allogeneic chondrocyt es. SMC from recipients of allogeneic and subsequent syngeneic transplants were strongly stimulated by both syngeneic and allogeneic chondrocytes, alt hough stimulation by the latter was significantly more pronounced. Sera fro m naive rats usually contained cytotoxic antichondrocyte antibodies but the ir level varied considerably in various individuals. In rats chosen as tran splant recipients on the basis of low antichondrocyte cytotoxicity of their sera, this toxicity was markedly raised after sensitization with allo- and syngeneic chondrocytes. Absorption with thymocytes or fibroblasts decrease d but did not abrogate cytotoxicity. These observations support previous re ports suggesting expression of tissue-specific antigen(s) by chondrocytes.