Gamma delta T cells assist alpha beta T cells in adoptive transfer of contact sensitivity

Cutaneous immune responses to contact sensitizers such as picryl chloride or oxazolone, are classical manifestations of T cell-mediated immunity in vivo. In fact, the first documentation of T cell-mediated immunity was the ability to adoptively transfer contact sensitivity (CS) responses. Although it is now clear that Ag/MHC-restricted alpha beta TCR positive effector T cells are responsible for 24 to 48 h CS responses, other subsets of Thy-1+ cells in mice also participate in the elicitation of CS. Thus, Thy-1+, CD5+, CD3-, B220+, hapten-specific, non-MHC-restricted early-acting cells are required to initiate CS responses by leading to local serotonin release, which allows for extravascular recruitment of the late-acting, alpha beta TCR+, CS effector T cells. This study describes another T cell population that is needed for the adoptive transfer of CS by alpha beta T cells. In vitro treatment of a mixture of CS effector cells with hamster mAb to gamma delta TCR, together with rabbit complement, or by panning on anti-hamster Ig-coated dishes, diminished substantially the subsequent transfer of CS reactivity without affecting either CS-initiating cells, or the later-acting, alpha beta TCR+ CS effector T cells. Immune cells treated with anti-alpha beta TCR mAb, or recovered as adherent cells from petri dishes after anti-gamma delta TCR panning (i.e., gamma delta TCR-enriched cells), reconstituted the ability of anti-gamma delta TCR-treated immune cells (i.e., alpha beta TCR-enriched cells) to transfer 24-h CS responsiveness. The phenotype of the gamma delta T cells that assisted CS effector alpha beta T cells was: CD3+, CD4-, and CD8+. The gamma delta T cells that assisted alpha beta T cells were not Ag-specific since anti-alpha beta-TCR-treated cells (gamma delta T-enriched) from picryl chloride immunized donors aided alpha beta T cells (anti-gamma delta TCR-treated) from oxazolone-immunized donors, and conversely gamma delta T cells from oxazolone-immunized donors aided alpha beta T cells from picryl chloride immunized donors. Furthermore, the CS-regulating gamma delta T cells were not MHC-restricted because gamma delta T cells from H2d or H2b donors could assist alpha beta T cells from H2k donors. It was concluded that a regulatory population of non-Ag specific, non-MHC-restricted gamma delta T cells was needed to assist immune effector, Ag/MHC-specific alpha beta T cells in the adoptive transfer of CS.