PEYERS PATCH CD8(-CELLS SECRETE T-HELPER TYPE-1 AND TYPE-2 CYTOKINES AND PROVIDE HELP FOR IMMUNOGLOBULIN SECRETION() MEMORY T)

Analysis of cytokine gene expression by reverse transcription-polymera se chain reaction (RT-PCR) demonstrated high spontaneous levels of tra nscripts for multiple cytokines in murine Peyer's patches (PP) compare d to spleen and peripheral lymph nodes. This is consistent with the pr esence of active germinal centers in PP and their continuous exposure to lumenal antigen including bacterial endotoxin. RT-PCR analysis of c ytokine transcripts in purified PP T cell populations revealed the pre sence of transcripts for interleukin-4(IL-4), IL-5 and IL-10 in additi on to interferon-gamma (IFN-gamma) in CD8(+) cells purified by now cyt ometry. The majority of PP CD8(+) T cells were also CD45RB(lo) (MB23G2 (-)), suggesting that these cells were activated/memory cells. CD8(+) cells in spleen and mesenteric lymph nodes (MLN) were predominantly CD 45RB(hi) (MB23G2(+)) consistent with a resting/naive phenotype. PP and MLN CD8(+) T cells also secreted IL-5 and IL-10 when stimulated with anti-CD3 monoclonal antibody and when co-cultured with PP B cells enha nced secretion of both IgG and IgA. These studies suggest that CD8(+) T cells at mucosal sites secrete T helper type 2 cytokines and can pro vide functional help for B cells in these tissues.