Suppression of alloreactivity with gamma delta T-cells: relevance to increased gamma delta T-cells following bone marrow transplantation.

Several reports have shown that an increase in T-cell receptor gamma/delta-positive T-cells (gamma delta T-cells) have been observed following bone marrow transplantation. gamma delta T-cells expanded from peripheral blood mononuclear cells from normal volunteers were used to investigate the function of gamma delta T-cells in vitro. Peripheral blood mononuclear cells were cultured with synthetic ligand of gamma delta T-cells, monoethyl phosphates (MEP), for 7 days. MEP specifically expanded gamma delta T-cells. Expanded gamma delta T-cells from subject "B" were added to an A anti-B or A anti-C mixed lymphocyte culture (MLC) containing responder cells from subject "A" and irradiated stimulator cells from subjects "B" or "C". The cultures were harvested on day 6 and tested for cytotoxicity against stimulator-type Con A blasts. gamma delta T-cells from subject "B" specifically inhibit generation of allospecific cytotoxic T lymphocytes (CTL) in A anti-B MLC. The results indicate that gamma delta T-cells exhibit veto-type suppression of alloreaction. If the current experiments are also applicable in vivo, gamma delta T-cells originating from the donor after bone marrow transplantation may inhibit graft rejection by suppressing recipient anti-donor reactivity. gamma delta T-cells may be involved in the suppression of allogeneic reaction in vivo following allogeneic bone marrow transplantation.