Orally induced tolerance generates an efferently acting suppressor T cell and an acceptor T cell that together down-regulate contact sensitivity.

Intragastric administration of the hapten trinitrochlorobenzene (TNCB) suppresses development of contact sensitivity (CS) to attempted epicutaneous sensitization with TNCB. Suppression induced by feeding TNCB is hapten specific and can be transferred to normal animals with lymphoid cells from fed mice. The lymphoid cells in hapten-fed mice that cause suppression of CS have been identified as Thy-1.2-positive cells in spleen and mesenteric nodes. The suppression with Peyer's patch cells from hapten-fed mice appears to be attributable to cells bearing Thy-1.2 antigen (T cell) and to cells with surface Ig (B cell). Feeding TNCB induces an efferent-acting suppressor T cell (Ts eff), as well as an intermediary acceptor T cell (T acc) with which it interacts to block adoptive transfer of CS with immune cells. Ts eff emanating from hapten-fed mice was identified by its specificity for the hapten, insensitivity to pretreatment with cyclophosphamide (CY), ability to produce soluble suppressor factor (SSF), and requirement for T acc to be functional. The presence of T acc in hapten-fed mice, on the other hand, was confirmed by its sensitivity to treatment with CY, interaction with Ts eff or SSF, and the ability to produce nonspecific inhibitor of TDTH cells. Thus, the suppressor T cells that are induced by administering the hapten intragastrically appear to function much like the cells of the suppressor T cell cascade that are induced by giving hapten via parenteral routes.