TH1 AND TH2 CELL INVOLVEMENT IN IMMUNE-RESPONSE TO SALMONELLA-TYPHIMURIUM PORINS

In understanding the regulation of the specific immune response to Sal monella typhimurium, the role of a surface major component (porins) wa s studied. In this study we demonstrate that purified porins are able to induce a different response to that induced by the porins present o n the S. typhimurium cell surface. Porin-treated or orally infected mi ce show anti-porin antibodies with bactericidal activity. The complete adoptive transfer of resistance to S. typhimurium is achieved only us ing splenic T cells from survivor mice after experimental infection. A fter stimulation with specific antigen in vitro CD4(+) cells from pori n-immunized mice released large amounts of interleukin-4 (IL-4), at a time when CD4(+) cells from S. typhimurium-infected mice predominantly secreted interferon-gamma (IFN-gamma). Limiting dilution analysis sho wed that infection resulted in a higher precursor frequency of IFN-gam ma-producing CD4(+) T cells and a lower precursor frequency of IL-4-pr oducing CD4(+) T cells, while immunization with porins resulted in a h igher precursor frequency of IL-4-producing cells and a low frequency of IFN-gamma-producing cells. Analysis of polymerase chain reaction-am plified cDNA from the spleens of infected mice revealed that IFN-gamma , IL-2 and IL-12 p40 mRNA were found 5 days after in vitro challenge a nd increased after 15 days; IL-10 expression was barely present after both 5 and 15 days, while IL-4 mRNA expression was not detected. In im munized mice, the IL-4 mRNA expression increased after 15 days, IFN-ga mma mRNA expression disappeared entirely after 15 days, while IL-2, IL -10 and IL-12 mRNA remained relatively unchanged.