Immunoregulatory lymphokines in rheumatoid joints. I. Search for interleukin 2 in synovial fluid

Since there have been conflicting findings about the presence of interleukin 2 (IL-2) in synovial fluid (SF) of patients with rheumatoid arthritis (RA), we decided to study this subject ourselves. In a sensitive assay utilizing CTLL-2 as indicator cells, no IL-2-like activity was found in SF from any of the 15 RA patients studied. Treatment of SF with hyaluronidase, dialysation, heating to 56 degrees C for 1 h, preincubation of CTLL-2 with SF prior to washing and incubation all resulted in no detection of any IL-2. SF itself did not inhibit the CTLL-2 assay. Failure to detect IL-2 may to some extent be explained by in vivo absorption of any IL-2 by IL-2 receptor-positive T cells in SF. The failure is discussed along with new evidence from various reports suggesting that impaired IL-2 production by activated T cells may be a feature of several autoimmune diseases.