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

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.