The Detection of a Putative IL-2 Inhibitor and of an IL-2 Facilitator Present in the Synovial Fluid of Patients with Rheumatoid Arthritis
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The synovial fluid of patients with rheumatoid arthritis was fractionated with ammonium sulfate and tested for facilitation or inhibition of IL-2 activity. IL-2 activity was measured by following the incorporation of tritiated thymidine into a cytotoxic T cell lymphoma line when cultured with the various fractions. It was found that facilitation of IL-2 activity by one fraction of the synovial fluid was apparent. Inhibition of IL-2 activity by a second fraction was found in isolated instances. One of the cell lines used, grown in equine serum, was found to be much more sensitive to IL-2 than the conventional line, grown in fetal bovine serum. Both lines, when cultured for two days in IL-2, secreted a factor which inhibited their own growth.