Alloreactivity and immunosuppressive properties of articular chondrocytes from osteoarthritic cartilage.

PURPOSE: To determine whether articular chondrocytes derived from osteoarthritic knee joints could evoke alloreactive proliferation of peripheral blood mononuclear cells (PBMC) and inhibit mitogenic activity of polyclonally activated CD4+ major histocompatibility complex (MHC) class II- restricted T cells in vitro.
METHODS: Osteoarthritic cartilages of 17 patients aged 61 to 85 years were harvested during total knee arthroplasty. Chondrocytes were cultured for experiments. PBMCs, CD4+ T cells, CD8+ T cells, and CD14+ monocytes from healthy subjects were also used. To investigate the allogeneic response and immunosuppressive properties of chondrocytes, assays for one-way mixed lymphocyte reaction (MLR), apoptosis, activated CD4+ T-cell proliferation, and cytotoxic CD8+ T-cells were performed. Chondrocyte cell-surface antigens were examined using flow cytometry.
RESULTS: Chondrocytes failed to trigger an allogeneic PBMC reaction and did not induce apoptosis of allogeneic PBMCs in the MLR assay. Chondrocytes inhibited the proliferation of polyclonally activated CD4+ T cells via cell-cell contact and escaped the allogeneic cytotoxic reactivity of CD8+ T cells. Chondrocytes expressed MHC class I but not MHC class II molecules or B7-1/-2-positive co-stimulatory molecules.
CONCLUSION: Chondrocytes from osteoarthritic knees in older patients exhibited similar immunomodulatory properties in vitro to those in juveniles or adults.