IMMUNITY TO EXPERIMENTAL SALMONELLA-TYPHIMURIUM INFECTIONS IN RATS - TRANSFER OF IMMUNITY WITH PRIMED CD45RC(-) CD4 T-CELL SUBPOPULATIONS()AND CD45RC()

The protective effect of primed CD4 T cells against a lethal dose of S almonella typhimurium was studied in Lewis rats. Primed CD4 T cells we re obtained by inoculating Lewis rats with a non-lethal dose of S. typ himurium. Four weeks after the infection, spleen CD4 T cells were sepa rated by antibody-coated magnetic microspheres using an antibody again st the CD4 molecule (W3/25). The cells were separated according to the ir expression of the CD45RC isoform of the leukocyte common antigen by FAGS. CD45RC(+) and CD45RC(-) CD4 T-cell subpopulations were transfer red to untreated rats 24 h prior to infection with S. typhimurium. Tra nsfer of CD45RC(+) and CD45RC(-) CD4 T cells induced a significant sur vival, p=0.022 and p=0.023 respectively, following inoculation with S. typhimurium compared to animals with no cells transferred. The infect ion induced an increase in CD4 T cells expressing the CD45RC isoform c ompared to untreated controls (p<0.001). It is concluded that both CD4 5RC(+) and CD45RC(-) cells can induce a significant protection against S. typhimurium infections in rats. Therefore the CD45RC antigen canno t be used as a phenotypic marker for functionally distinct CD4 T-cell subpopulations. The infection-induced increase in CD45RC(+) cells is m ost likely due to generation of antigen-specific memory T cells.