Influence of sera from tumor bearing mice on immune reaction.

Immunopotentiation abilities of sera from mice bearing fibrosarcoma or lymphoma for various periods of time were assayed using the plaque forming cell (PFC) technique. The influence of such sera on cell proliferation, evaluated by the spleen index, was determined in lethally irradiated mice reconstituted with syngeneic bone marrow cells. Sera from tumorous animals stimulated the number of PFC significantly, fibrosarcoma sera being more effective in the advanced stage and lymphoma in the initial phase. Sera from mice with both tumors in the early phase increased spleen indices significantly, and sera from mice with advanced tumors were less effective. The possible role of lymphokines in these events is discussed.