Deficiency of IL-5 Receptor α-Chain Selectively Influences the Development of the Common Mucosal Immune System Independent IgA-Producing B-1 Cell in Mucosa-Associated Tissues

Abstract

Deletion of IL-5Rα-chain (IL-5Rα−/−) selectively influenced the mucosal IgA responses in vivo. While levels of IgA in mucosal secretions were more reduced in IL-5Rα−/− mice than in wild-type mice, the levels of IgA in serum were not changed. The frequency of IgA-producing cells was reduced in mucosal effector sites (e.g., intestinal lamina propria and nasal passage), but not in inductive sites such as Payer’s patches and nasal-associated lymphoreticular tissues in IL-5Rα−/− mice. IgA-committed (surface IgA+; sIgA+) B-1 cells mainly resided in mucosal effector tissues, while conventional sIgA+ B (B-2) cells formed in mucosal inductive sites of wild-type mice. In contrast, in the effector tissue of IL-5Rα−/− mice, sIgA+ B-1 cells, but not sIgA+ B-2 cells in the inductive site, were significantly reduced. IL-5Rα was more expressed on sIgA+ B-1 cells than was IL-6R, while both IL-5Rα and IL-6R were expressed on sIgA+ B-2 cells in wild-type mice. sIgA+ B-1 cells produced high levels of IgA with rIL-5 rather than of rIL-6 in vitro. Taken together, the findings suggest that the IL-5/IL-5R signaling pathway is critically important for the development of common mucosal immune system independent sIgA+ B-1 cell in mucosal effector tissues in vivo.