A PURIFIED PROTEIN FROM SALMONELLA-TYPHIMURIUM INHIBITS HIGH-AFFINITYINTERLEUKIN-2 RECEPTOR EXPRESSION ON CTLL-2 CELLS

Previously, we have demonstrated that the immunosuppression induced by the purified substance Salmonella typhimurium-derived inhibitor of T- cell proliferation (STI) involves T-cell non-responsiveness to interle ukin-2 (IL-2). In the present study, it was found that STI inhibited t he growth of CTLL-2 cells, which are an IL-2-dependent cytotoxic T-cel l line. Analysis of IL-2 receptor (IL-2R) function showed that STI inh ibited high-affinity receptor expression and internalization by CTLL-2 cells. Furthermore, FAGS analysis demonstrated that STI inhibited bot h beta chain and gamma chain expression of IL-2R on the cells. These r esults suggest that the suppression of T-cell proliferation induced by STI results from a defect in IL-2R function.