Deficiency of IL-5 receptor alpha-chain selectively influences the development of the common mucosal immune system independent IgA-producing B-1 cellin mucosa-associated tissues

Deletion of IL-5R alpha-chain (IL-5R alpha(-/-)) selectively influenced the mucosal IgA responses in vivo. While levels of IgA in mucosal secretions w ere more reduced in IL-5R alpha(-/-) mice than in wild-type mice, the level s of IgA in serum were not changed. The frequency of IgA-producing cells wa s reduced in mucosal effector sites (e.g., intestinal lamina propria and na sal passage), but not in inductive sites such as Payer's patches and nasal- associated lymphoreticular tissues in IL-5R alpha(-/-) mice. IgA-committed (surface IgA(+); sIgA(+)) B-1 cells mainly resided in mucosal effector tiss ues, while conventional sIgA(+) B (B-2) cells formed in mucosal inductive s ites of wild-type mice. In contrast, in the effector tissue of IL-5R alpha( -/-) mice, sIgA(+) B-1 cells, but not sIgA(+) B-2 cells in the inductive si te, were significantly reduced, IL-5R alpha was more expressed on sIgA(+) B -1 cells than was IL-6R, while both IL-5R alpha and IL-6R were expressed on sIgA(+) B-2 cells in wild-type mice. sIgA(+) B-1 cells produced high level s of IgA with rIL-5 rather than of rIL-6 in vitro. Taken together, the find ings 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.