This investigator has recently provided evidence that oral delivery of protein antigens to mice, in concert with the adjuvant cholera toxin (CT), induced T helper type 2 (Th2) cells in Peyer's patches and in spleen, and resulted in mucosal IgA and serum IgG1 and IgE antibody isotypes characteristic of Th2-type responses. A major goal of this renewal application will be to define the molecular basis for Th cell-mediated and humoral B-cell responses to well defined oral immunogens. Despite intensive recent study, the relative contributions of Th1-type and Th2-type cells and derived cytokines for mucosal IgA and systemic antibody or cell-mediated immune (CMI) responses are not well understood. This is due in part to our incomplete understanding of the contributions of major antigen-presenting cells in the Peyer's patches, e.g., macrophages (MO), dendritic cells (DC), and class II+ B-cells for the induction of Th1/Th2 cells for IgA responses. Further, the underlying mechanisms for signal transduction pathways in mucosal Th1 and Th2 cells has never been addressed. In this renewal application, the first specific aim will use the adjuvants CT and E. coli labile toxin (LT) versus rIL-12 and rSalmonella expressing proteins to establish the precise role of Th2 and Th1 cells for mucosal immune responses, respectively. Unique CD4+ Th cell clones will be derived from both normal and cytokine knockout (IFN-g -/-, IL-4 -/-, IL-6 -/- and IL-10 -/-) mice for study. The relative roles for MO, DC or class II+, surface IgA- positive (sIgA+) B-cells in Peyer's patches, for induction of CD4+ Th cells and the role of second signals in T-cell activation will be given emphasis in the second aim. Construction of an antigen-specific sIgA+ B-cell hybridoma expressing class II and development of IgG-versus IgA B-cell anti-ovalbumin transgenic mice will facilitate this effort.
The third aim will define the signal transduction pathways involved in mucosal activation of Th1-type versus Th2-type cells.
The fourth aim will focus on cytokine-specific gene promoters and their mRNA expression in Th cell subsets which result from an adjuvant-induced mucosal response. The final specific aim will focus on the role of Th2 cells and their cytokines for regulation of mucosal immunity in vitro and in vivo. These studies will take advantage of alpha/beta TCR -/- mice, which lack mucosal IgA plasma cells, as adoptive hosts for CD4+ Th cell clones for analysis of antigen-specific mucosal IgA responses.
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