Interleukin 2 enhancement of veto suppressor cell function in T-cell-depleted bone marrow in vitro and in vivo.

In allogeneic bone marrow transplantation, graft-ver-sus-host disease can be prevented by the removal of T cells from the donor marrow. The risk of marrow graft rejection is however greater for T-cell-depleted marrow than nondepleted marrow. Cells with a specific type of suppressor activity, termed veto cells, which might depress the host rejection response, have been reported to be present in murine marrow. Among the cell populations that are able to mediate veto activity, there are subpopulations that do not express Thy; such subpopu-lations might therefore persist following T cell depletion. Since interleukin 2 is able to enhance certain activities of non-T-cells, the ability of interleukin 2 to enhance veto activity of T-cell-depleted marrow was investigated in vitro and in vivo. It was found that the incubation of T-cell-depleted marrow with interleukin 2 significantly increased veto activity as assessed by in vitro assays and also enhanced engraftment of MHC-mismatched, T-cell-depleted marrow in vivo.