Antigenicity and accessory cell function of human articular chondrocytes.

It is postulated that chondrocytes may be actively involved in the pathogenesis of inflammatory joint diseases, presumably by providing tissue specific antigens that may initiate or sustain autoimmune reactions. To investigate whether chondrocytes may also function as accessory cells in ongoing immune processes, mixed leukocyte-chondrocyte cultures and antigen presentation assays were studied. Freshly isolated and short term cultured HLA class II antigen (Ia) negative as well as gamma-interferon treated Ia positive chondrocytes were weakly or not stimulatory to allogeneic or autologous resting lymphocytes derived from either normal donors or patients with rheumatoid arthritis. In an antigen presenting system using tetanus toxoid, the majority of chondrocyte preparations tested induced an antigen driven response in HLA matched allogeneic or autologous resting T cells which, however, was much less when compared to blood monocytes. In contrast, using activated T cells derived from tetanus toxoid specific T cell lines, an efficient antigen presenting capacity could be demonstrated in both Ia positive and initially Ia negative chondrocytes. Interestingly, the latter population had acquired Ia antigens upon incubation with the T cell line.