Reaction of antibody to mycobacterial 65 kDa heat-shock protein with human chondrocytes.

We report on the reactivities of four monoclonal antibodies generated against mycobacterial proteins to human chondrocytes, cells in cartilage which may be subject to immune attack in rheumatoid arthritis. Only one of the monoclonal antibodies, ML30, which had been shown previously to react with a human homologue to heat-shock protein (hsp), reacted strongly to chondrocytes. By immunocytochemical methods using fixed chondrocytes, ML30 reacted to cytoplasmic constituents in a granular pattern. There were no marked qualitative differences in the staining intensities and patterns of chondrocytes kept at ambient temperatures and those subjected to 42 degrees C heat treatment. No significant staining was observed with normal peripheral blood mononuclear cells. By indirect immunofluorescence, the distribution of ML30 reactive constituents was very low on the cell surface. Reactivities of each of the monoclonal antibodies were tested on frozen sections of cartilage. Significant reactivity was found only with ML30, and the staining was only associated with chondrocytes, not with the cartilage matrix surrounding the cells. These findings may have significance in view of the possibility that an hsp homologue may be a target for inciting or perpetuating the autoimmune process in rheumatoid arthritis.