Role of interleukin-4 in down-regulation of contact sensitivity by gammadelta T cells from tolerized T-cell receptor alpha-/- mice.

Contact sensitivity (CS) is a classical example of an in vivo T-cell-mediated immune response that is under regulation. Such down-regulation can be mediated by alphabeta T cells in mice that are tolerized by prior exposure to high doses of antigen. In contrast, we demonstrated previously that such high-dose antigen tolerance in T-cell receptor (TCR) alpha-/- H-2d mice induced antigen-specific, apparently major histocompatibility complex-unrestricted, CD4- CD8- gammadelta T cells, that also could down-regulate CS responses antigen-specifically in vivo, and also inhibited in vitro production of IFN-gamma. In the present experiments we employed H-2b-deficient TCRalpha-/- and TCRbeta-/- mice, owing to different molecular constructs than were used previously, and confirmed that tolerized gammadelta T cells in these different H-2b alphabeta TCR-/- mice down-regulated CS. Thus, gammadelta T-cell suppressor function was not limited to mice bearing a special transgenic TCRalpha-/- DNA construct. Furthermore, employing monoclonal antibody and complement depletion in vitro and adoptive transfer in vivo, characterized the phenotype of these gammadelta down-regulatory T cells as: CD3+, CD28+, CD40-ligand+, Fas+, FcgammaR+ and NK1.1-. Also, in vitro antigen desensitization of these trinitrophenyl (TNP)-specific TCRgammadelta+ down-regulatory cells was achieved with soluble TNP-bovine serum albumin (BSA), but not with oxazolone-BSA, showing that these suppressive gammadelta T cells have antigen-specific receptors. Moreover, employing monoclonal antibody blocking of gammadelta suppressors in vitro, and of recipients in vivo, we showed that interleukin-4 (IL-4) was involved in this down-regulation of CS by gammadelta T cells, while IL-10 and transforming growth factor-beta2 were not. In summary, generation of antigen-specific, double-negative, gammadelta suppressor cells, by tolerance of high antigen doses in TCRalpha-/- mice, appears to be a general phenomenon, and IL-4 production is involved in their down-regulation of the T helper type 1 cells that mediate CS.