Synovial Cells Responding to a 65‐kDa Mycobacterial Heat Shock Protein have a High Proportion of a TcRγδ Subtype Uncommon in Peripheral Blood

We have analysed the ability of T cells from synovial fluid mononuclear cells (SFMC) and from peripheral blood mononuclear cells (PBMC) of inflammatory arthritic diseases to proliferate in response to mycobacterial antigens (65‐kDa heal shock protein [hsp] of BCG. whole BCG) and to rat collagen type II. The SFMC demonstrated a significantly greater ability to respond to 65‐kDa hsp of BCG. and to whole BCG, compared with PBMC from the same patients, With collagen type II, only a small proportion of the patients showed a proliferative response, although with this antigen also SFMC responded better than PBMC. There was no difference between SFMC and PBMC in the response to control antigen (tetanus toxoid), phytohaemagglutinin (PHA), or interleukin 2 (IL‐2). A high proportion of cells in SFMC‐derived short‐term T‐cell lines were of TcRγδ type, often exceeding the number of TcRγδ type. There was a significantly higher proportion of TcRγδ cells in the SFMC lines compared with the PBMC lines, and a large part of the TcRγδ cells in she SFMC cultures was CD8⁺ The SFMC lines had a high proportion of δ‐ TCS‐1⁺ cells (Vδ1) among their TcRγδ cells, always exceeding the percentages of TiγA⁺ (Vγ9) and BB3⁺ (Vδ2) in the PBMC lines, the distribution of TcRγδ subtypes was markedly different, with a TiγA⁺/BB3⁺ population in the majority. These data argue for a different subpopulation distribution of TcRγδ cells in synovial fluid compared with peripheral blood of patients with inflammatory arthritic diseases.