Gross virus-induced lymphoma cells express strong virus-associated (Gross murine leukemia virus [G-MuLV]) antigens and are consistently rejected when grafted in normal adult syngeneic rats. By contrast, similar grafts are tolerated and allowed to grow progressively by rats that have been injected at birth with deaggregated G-MuLV antigens. However, the tolerance induced by this procedure is only partial as the grafted lymphoma cells lose their G-MuLV membrane antigens. These cells showing an antigenic disjunction, with negative membrane and positive cytoplasmic G-MuLV antigenic expression, become transplantable in normal-nonconditioned adult recipients. By further grafting, the expression of cytoplasmic G-MuLV antigens is similarly lost while the lymphoma cells substantially increase their transplantability, rate of growth, and capacity for metastasis.

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