ELISA for the detection of the lymphokine soluble immune response suppressor

Murine soluble immune response suppressor (SIRS) is a product of Ly 2+ suppressor T cells which is activated to SIRSox by peroxide produced by macrophages. SIRSox inhibits cell division by normal and transformed cell lines and antibody secretion by B lymphocytes. Rat monoclonal anti-SIRS antibodies were developed to determine if ELISA methodology could replace bioassays for quantitation of SIRS in biological samples. Purified SIRS, applied to nitrocellulose, was detected with an avidin-biotin-horseradish peroxidase system. This ELISA was capable of detecting pg quantities of SIRS and detected SIRS after fractionation by high performance liquid chromatography. However, SIRS in crude supernatant fluids was undetectable by this method, presumably due to the small percentage of SIRS protein in relation to total protein in these samples. Thus, a competitive ELISA was adopted which, in initial experiments, detected SIRS in impure sources. This competitive ELISA may be useful in evaluating the presence or absence of SIRS in various biological samples.