“…CD4 + o#[3 T cells have been shown to be essential for IgA B cell responses (for review see reference 20), whereas the results of this study suggest that ~//8 T cells also may regulate the mucosal IgA immune response. The helper T cells that preferentially produce IL-4, IL-5, IL-6, and IL-10, the Th2 subset of CD4 + cells, promote IgA responses (16,(21)(22)(23). Our earlier studies indicated that oral immunization of normal mice with the combined TT and CT vaccine induced Th2-type cells in the IgA mucosal response (16), and TCR-[3 -/-mice are essentially devoid of mucosal IgA-producing cells (Fujihashi, K., M.-N. Kweon, M. Marinaro, K. Imaoka, R.J. Jackson, J.R. McGhee, and H. Kiyono, manuscript in preparation).…”