The Lyt phenotype of the T cells in an antitumor adoptive transfer differs for "parent to F1" and "parent to parent" combinations.
The T-cell subset mediating tumor graft neutralization was characterized in a methylcholanthrene (MC) tumor system. Lyt 1+ cells were critical for the successful prevention of outgrowth of the tumor cells in graft neutralization assays with irradiated recipients. Elimination of Lyt 1+ cells abolished the outgrowth inhibitory effect exerted by T-cell-enriched populations derived from syngeneic or semisyngeneic mice immunized with the H-2-carrying MC-induced M-A tumor. In accordance, lymphocyte populations containing 98% Lyt 1+ cells derived from M-A-immune mice, mediated a complete transplantation immunity against this tumor. When the immune T cells admixed to the tumor inoculum were syngeneic to the recipient (i.e., A-derived cells were transferred to A recipients, or F1 to F1), elimination of the Lyt2+ cells did not influence the potential to inhibit tumor outgrowth. The presence of Lyt 1+2- cells were thus necessary, and sufficient, in the syngenic combination. A reduction of the graft-inhibiting potential occurred after elimination of Lyt 2+ cells from the A-derived M-A immune T-cell population when the recipients were semisyngeneic (i.e., (A/Sn X A.SW)F1, (A/Sn X CBA)F1, or (A/Sn X C57B1/6)F1). Consequently, only in the semisyngeneic, but not in the syngeneic combinations, was the transfer of Lyt 2+ cells necessary for optimal graft inhibition. It can be concluded that the genotypic relation between the donor and the recipient influences the prerequisites of the tumor cell neutralization.