Differences in epitopes recognized by T cells during oral tolerance and priming

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Abstract
Feeding protein antigens to mice normally leads to the development of oral tolerance but under some circumstances, feeding can lead to immunity, for example, following pretreatment of mice with cyclophosphamide (CY). In both cases, however, it is possible to detect sensitized T cells in the spleen and mesenteric lymph nodes (MLN) by in vitro lymphokine release for granulocyte-macrophage-CSF (GM-CSF) and IFN-. This study examines the recognition of the immunodominant T cell epitope on ovalbumin (OVA) following intragastric priming and tolerance. T cells from CY/OVA treated mice and cells from mice injected subcutaneously with OVA in CFA responded well to both OVA and the H2d restricted peptide epitope pOVA323–339 releasing GM-CSF. On the other hand MLN or spleen T cells from tolerized mice which responded to the protein in vitro did not recognize the immunodominant determinant. The cells responding from tolerized mice were restricted by the class II MHC so these results show there can be differential recognition of T cell epitopes between oral priming and tolerance.