EXPRESSION OF ICAM-1 ON INTACT CARTILAGE AND ISOLATED CHONDROCYTES

A major factor in cellular cytotoxicity is the interaction between LFA -1 on leukocytes and ICAM-1 on targets. Because several inflammatory c artilage diseases are characterized by the presence of leukocyte infil trates, the expression of ICAM-1 on human cartilage, cultured chondroc ytes, and transplanted cartilage was investigated using monoclonal ant ibodies. Frozen tissue sections, chondrocytes in suspension, as well a s total cellular mRNA were prepared from human cartilage samples. ICAM -1 expression was studied with two different monoclonal antibodies dir ected against ICAM-1 by immunohistochemical APAAP-staining and additio nal flow cytometric analyses. The expression of ICAM-1-mRNA in cartila ge tissue was analyzed using the northern blot hybridization technique . Furthermore, chondrocytes were treated in culture with interleukin-1 (IL-1) and gamma-interferon (gamma-IFN). ICAM-1 expression after cult ure was quantified using flow cytometric analysis. We could detect ICA M-1 mRNA in cartilage tissue, however, the immunostaining of tissue se ctions using monoclonal antibodies did not give clear positive reactio ns. Isolated chondrocytes showed strongly positive staining patterns i n comparison with adequate negative controls as assessed by flow cytom etry. A dose-dependent increase of the expression of ICAM-1 on chondro cytes was observed when stimulated with IL-1 and gamma-IFN. Finally, t wo of the three studied transplanted autologous cartilage samples with advanced resorption showed the presence of ICAM-1 molecules as assess ed by immunohistochemistry. This expression of ICAM-1 suggests that th e molecule plays a role in severe cartilage inflammatory processes, wh ere tissue damage leads to the exposure of chondrocyte surfaces.