A bone marrow-derived APC in the gut-associated lymphoid tissue captures oral antigens and presents them to both CD4(+) and CD8(+) T cells

We have previously reported that feeding OVA to C57BL/6 mice can lead to a weak CTL response that is dependent on CD4(+) T cell help and is capable of causing autoimmunity. In this study, me investigated the basis of the clas s I and class II-restricted Ag presentation required for such CTL induction . Two days after feeding OVA, Al-specific CD4(+) and CD8(+) T cells were se en to proliferate in the Peyer's patches and mesenteric lymph nodes. Little proliferation,vas evident in other lymphoid tissues, except at high Ags do ses, in which case some dividing CD4(+) T cells were observed in the spleen and peripheral lymph nodes. Using chimeric mice, the APC responsible for p resenting orally derived Ags was shown to be derived from the bone marrow. Examination of the Ag dose required to activate either CD4(+) or CD8(+) T c ells indicated that a single dose of 6 mg OVA was the minimum dose that con sistently stimulated either T cell subset. These data indicate that oral Ag s can be transported from the gut into the gut-associated lymphoid tissue, where they are captured by a bone marrow-derived APC and presented to both CD4(+) and CD8(+) T cells.