DIFFERENCES IN EPITOPES RECOGNIZED BY T-CELLS DURING ORAL TOLERANCE AND PRIMING

Feeding protein antigens to mice normally leads to the development of oral tolerance but under some circumstances, feeding can lead to immun ity, for example, following pretreatment of mice with cyclophosphamide (CY). In both cases, however, it is possible to detect sensitized T c ells in the spleen and mesenteric lymph nodes (MLN) by in vitro lympho kine release for granulocyte-macrophage-CSF (GM-CSF) and IFN-gamma. Th is study examines the recognition of the immunodominant T cell epitope on ovalbumin (OVA) following intragastric priming and tolerance. T ce lls from CY/OVA treated mice and cells from mice injected subcutaneous ly with OVA in CFA responded well to both OVA and the H2(d) restricted peptide epitope pOVA(323-339) 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 r esponding from tolerized mice were restricted by the class II MHC so t hese results show there can be differential recognition of T cell epit opes between oral priming and tolerance.