Antigen-specific Treg cells

A variety of studies indicate that stable Foxp3 expression is sufficient to confer a regulatory T-cell phenotype to CD4 T cells [11-13]. Thus, retroviral Foxp3 transduction is a valuable means to endow antigen-specific T cells with a regulatory phenotype. This represents an important tool because, unlike the in vitro expansion [14, 15] of Tregs preformed in vivo, it allows to produce Tregs of any desired specificity. 

Suppression of the DTH Response The induction and regulation of CD8+ Tregs in vivo is complex and dependent on several cell types [2,3], In vivo, the induction of CD8-I- suppressor T cells required Lyt-l-l- (CD4) suppressor-inducer T cells that did not directly suppress DTH. The mechanism of this induction was not clear but appeared to be mediated by antigen-specific, soluble molecules produced by the suppressor-inducer T cells [18]. Additionally, the in vivo induction of CD8+ suppressor T cells requires cells sensitive to the cytotoxic effects of cyclophosphamide [19,20]. 

Double negative (CD4-CD8-) TCR-ap-f Treg cells that mediate tolerance in several experimental autoimmune diseases have been described [ 111 ]. These double negative T cells are specific for MHC class I molecules and the suppressive effect of these cells on the proliferation and cytotoxic activity of CD8-I- T cells with the same antigen specificity was not mediated by cytokines, but instead was attributed to Fas-mediated apoptosis of alloreactive T cells [112]. 

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