CD4(+) BUT NOT CD8(+) T-CELLS ARE REQUIRED FOR THE INDUCTION OF ORAL TOLERANCE

It has been suggested that oral tolerance is mediated by CD8(+) T lymphocytes, but the functional properties of these cells are unclear. Here we show that the induction of tolerance by feeding mice ovalbumin (OVA) does not prime antigen-specific class I MHC-restricted cytotoxic T cells in vivo. Indeed, such responses are markedly suppressed in mice fed OVA, and the induction of oral tolerance is abolished by depletion in vivo of CD4(+) but not CD8(+) T cells. These results indicate that CD8(+) lymphocytes are unlikely to play a major role in the induction of oral tolerance and are the first demonstration that specific cytotoxic responses to an exogenous antigen can be suppressed by feeding antigen.