Evidence for a T suppressor cell-inducing antigenic determinant shared by ADJ-PC-5 plasmacytoma and syngeneic BALB/c spleen cells

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Abstract
The BALB/c plasmacytoma ADJ-PC-5 induces in early stages of tumorigenesis specific T suppressor (Ts) cells apparently as the first reaction of the immune system towards the growing tumor. In attempts to apply the concept of early induction of Ts cells in neoplasia for the induction of tolerance to allografts we have tried to induce Ts cells against alloantigens by injecting allogeneic spleen cells in doses increasing exponentially from 10 to 105 cells/mouse. Experiments using various strain combinations failed to demonstrate induction of specific Ts cells by this procedure. To explain the apparent discrepancy between these and the tumor data the capacity of the ADJ-PC-5 tumor cells to induce Ts cells in allogeneic combinations was analyzed. ADJ-PC-5 cells are capable of inducing specific Ts cells in CBA/J mice. These Ts cells specifically suppress the induction of a primary cytotoxic T cell response of CBA/J spleen cells against BALB/c, BALB.B and (BALB/c × C57BL/6)Fl cells but not one against B10.D2 or C57BL/10 target cells. The ADJ-PC-5-induced CBA/J Ts cells have been further analyzed using a panel of different target or responder cells. From these experiments the following conclusions can be drawn: the CBA/J Ts cells are specific for an antigen which is shared by ADJ-PC-5 and normal BALB/c spleen cells. The antigen in question is not coded for by the H-2d major histocompatibility complex. The data suggest that the Ts cell-inducing antigen on ADJ-PC-5 tumor cells is not a tumor associated neoantigen but a self antigen also present on normal BALB/c lymphoid cells.