IMMUNE-RESPONSES TO WEAKLY IMMUNOGENIC VIRALLY INDUCED-TUMORS .5. SHORT INVITRO CULTIVATION OF YAC CHANGES ITS ANTIGENIC PROPERTIES

YAC tumor, a Moloney virus-induced lymphoma of A mice, considerably changed its immunogenic properties following cultivation for 12-14 h in vitro. The cultivated tumor, designated YAC-1, generated anti-YAC and anti-YAC-1 reactive cells, while the original YAC tumor generated suppressor cells with abrogated anti-YAC and anti-YAC-1 cytotoxic responses. Cold target competition experiments demonstrated that YAC-1 and YAC tumors have distinctive antigenic structures on their surfaces. RBL5, a Rauscher virus-induced lymphoma of C57BL/6 mice, generated anti-YAC, anti-YAC-1 and anti-RBL5 reactive cells in A mice. YAC-1 generated reactive cells against the allogeneic RBL5 tumor. The total population of antitumor reactive cells contained separate subpopulations directed maximally toward each of the 3 target tumors. The subpopulation was partially, but not completely, cross-reactive with the other tumors. RBL5 priming and YAC-1 priming stimulated separate populations of antitumor reactive cells.