A cell-free Salmonella typhimurium extract modulates interleukin-2 (IL-2) receptor expression but not IL-2-stimulated responses of murine splenic lymphocytes.
In a previous study, we observed that a cell-free Salmonella typhimurium extract induced suppression of mitogen-induced T-cell proliferation and this suppression involved non-responsiveness of T-cells to interleukin-2 (IL-2). In this study, we found that a cell-free S. typhimurium extract modulated IL-2 receptor (IL-2R) expression on phytohemagglutinin (PHA)-stimulated murine spleen cells and this was a mechanism of T-cell non-responsiveness to IL-2, but did not affect IL-2 binding to IL-2R and the consequent responses. Western blotting using anti-phosphotyrosine antibodies showed that IL-2R-mediated tyrosine phosphorylation of protein substrates in PHA-activated murine splenic T-cells, which express a high-affinity IL-2R (alpha- and beta-chains), was not affected by treatment with the S. typhimurium cell-free extract. Furthermore, PHA-activated spleen T-cells responded to recombinant IL-2 and this was not inhibited by the extract. Surprisingly, IL-2R expression was augmented by treatment with the extract, although this was independent of IL-2 production. These results suggest that the suppression of T-cell proliferation induced by the Salmonella cell-free extract was associated with augmentation of IL-2R expression, rather than down-regulation of the IL-2 response. This may be a mechanism responsible for the Salmonella extract-evoked suppression of mitogen-induced T-cell proliferation.
Matsui
K
K
Department of Microbiology, Meiji College of Pharmacy, Tokyo, Japan.
Arai
T
T
D000818:Animals; D007108:Immune Tolerance; D007376:Interleukin-2 / Q000502:physiology*; D008213:Lymphocyte Activation; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D015375:Receptors, Interleukin-2 / Q000032:analysis* / Q000502:physiology; D012486:Salmonella typhimurium / Q000502:physiology*; D013601:T-Lymphocytes / Q000276:immunology*
D007376:Interleukin-2; D015375:Receptors, Interleukin-2