Immune response to sheep red cells in AKR mouse leukemia.

Long-term administration of sheep red cells to AKR mice did not influence the development of spontaneous leukemia. In mice with transplanted leukemia there was an increase in numbers of spleen hemolytic plaque-forming cells (PFC) during the early leukemic phase, as compared to controls, and a marked decrease and final disappearance of PFC from all lymphoid organs in the late leukemic phase. This pattern was seen in both the primary and secondary immune responses. The time course of PFC response in both the primary and the secondary response was similar to that of controls in the early leukemic phase, while there was only a negligible response without a peak in the late leukemic phase. The early increase in PFC was observed only in mice that received viable leukemic cells and not in mice injected with other cell preparations. The absence of PFC in late leukemia did not appear to be caused by an interaction between leukemic and normal cells in the assay procedure.