CD4–c‐kit–CD3ϵ–IL‐2Rα+ 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

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Abstract
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 CD3ϵ–IL‐2Rα+ cells purified from the Thy1.2–B220– fraction of PP cells secreted IL‐5 when stimulated with IL‐2. CD3ϵ–IL‐2Rα+ cells were subdivided into CD4+ and CD4– populations or c‐kit+ and c‐kit– populations, and only the CD4– and c‐kit– CD3ϵ–IL‐2Rα+ cells secreted IL‐5 in response to IL‐2. CD3ϵ–IL‐2Rα+ cells did not express NK cell‐markers and exhibited a lymphoid morphology. We have therefore identified CD3ϵ–IL‐2Rα+ 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 CD3ϵ–IL‐2Rα+ cells from PP resulted in reduced IL‐5 production. Furthermore, IgA secretion by B cells was increased when PP B cells were cocultured with CD3ϵ–IL‐2Rα+ cells. Taken together, these results suggest that the novel subset of CD4–c‐kit–CD3ϵ–IL‐2Rα+ 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.