CD4(-CELLS ARE REQUIRED FOR THE INDUCTION OF ORAL TOLERANCE() BUT NOTCD8(+) T)

It has been suggested that oral tolerance is mediated by CD8(+) T lymp hocytes, but the functional properties of these cells are unclear. Her e we show that the induction of tolerance by feeding mice ovalbumin (O VA) 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 depletio n in vivo of CD4(+) but not CD8(+) T cells. These results indicate tha t CD8(+) lymphocytes are unlikely to play a major role in the inductio n of oral tolerance and are the first demonstration that specific cyto toxic responses to an exogenous antigen can be suppressed by feeding a ntigen.