CD4(-)c-kit(-)CD3epsilon(-)IL-2Ralpha(+) Peyer's patch cells are a novel cell subset which secrete IL-5 in response to IL-2: implications for their role in IgA production.

In this study, we examined which cell population contributes to IL-5 production by Peyer's patch (PP) cells. Thy1.2(-) fraction of PP cells, but not those of splenocytes, secreted IL-5 in response to IL-2. We found that CD3epsilon(-)IL-2Ralpha(+) cells purified from the Thy1.2(-)B220(-) fraction of PP cells secreted IL-5 when stimulated with IL-2. CD3epsilon(-)IL-2Ralpha(+) cells were subdivided into CD4(+) and CD4(-) populations or c-kit(+) and c-kit(-) populations, and only the CD4(-) and c-kit(-) CD3epsilon(-)IL-2Ralpha(+) cells secreted IL-5 in response to IL-2. CD3epsilon(-)IL-2Ralpha(+) cells did not express NK cell-markers and exhibited a lymphoid morphology. We have therefore identified CD3epsilon(-)IL-2Ralpha(+) cells as a unique lymphoid population that are not classified into conventional IL-5-producing cell populations, such as T cells, mast cells and NK cells. Depletion of CD3epsilon(-)IL-2Ralpha(+) cells from PP resulted in reduced IL-5 production. Furthermore, IgA secretion by B cells was increased when PP B cells were cocultured with CD3epsilon(-)IL-2Ralpha(+) cells. Taken together, these results suggest that the novel subset of CD4(-)c-kit(-)CD3epsilon(-)IL-2Ralpha(+) PP cells are capable of secreting a high level of IL-5 in response to IL-2, contribute markedly to IL-5 production and help IgA secretion by B cells.