Naïve CD4+ T cells of Peyer's patches produce more IL-6 than those of spleen in response to antigenic stimulation.

Peyer's patches (PPs) are potential sites where specific mucosal immune responses and oral tolerance are induced. The unique features of these immune responses are thought to occur in micromilieu and are largely affected by antigen-presenting cells (APCs) such as dendritic cells. In this study, we investigated the cytokine profiles induced by the activation of CD4(+) T cells of PPs. PP cells from TCR transgenic mice secreted greater amounts of IL-5 and IL-6 than spleen cells after antigenic stimulation. IL-5 was mainly produced by PP non-T cells, whereas IL-6 was secreted by PP CD4(+) cells. PPs contained two major populations including naïve and memory/activated CD4(+) cells; both populations secreted IL-6 upon activation. We also found that CD4(+)/CD62L(hi) naïve cells from PPs secreted a greater amount of IL-6 after stimulation than those from the spleen. Furthermore, subtraction and qPCR analyses revealed that PP CD4(+)/CD62L(hi) cells express a greater amount of transcripts of GA-binding protein β subunit 1 than those of the spleen. These results suggest that naïve T cells as well as non-T cells and activated/memory T cells from PPs are distinct from their splenic counterparts and thus cause unique immune responses the in intestine.