Both T and non-T cells with proliferating potentials are effective in inducing suppression of allograft responses by alloantigen-specific intravenous presensitization combined with suboptimal doses of 15-deoxyspergualin.

In an MHC class I-disparate combination of mouse strains, a single intravenous injection of donor spleen cells combined with 10 suboptimal doses of 15-deoxyspergualin (DSG) administration was effective in inducing donor-specific suppression of cytotoxic T-lymphocyte (CTL) responses and prolonged survival of the relevant skin allograft. Proliferative potentials of the donor spleen cells were requirement for the induction of suppressed allospecific responses, but both highly purified T cells and non-T cells were equally effective to induce the suppression of CTL responses by intravenous injection. These results have shown that, although working on different mechanisms, DSG is as effective as FK506 or rapamycin in inducing allograft tolerance when used at suboptimal doses along with the donor-specific intravenous presensitization, and an immune mechanism other than well-characterized veto T cells is working in this model in suppressing alloreactive CTL precursors.