Purpose: The mechanism underlying the immunomodulation caused by blood transfusion has yet to be elucidated. The aim of the present study was to determine whether the transfusion of a soluble or insoluble factor present in stored blood can induce immunomodulation, which would thereby promote solid tumor growth.
Methods: C57Bl/6J mice were subcutaneously inoculated with B16-CG melanoma cells, which secrete beta-human chorionic gonadotropin (beta-hCG). Following inoculation, each of three different products of allogeneic and syngeneic blood were transfused on days 0 and 1: fresh whole blood, stored whole blood, and supernatants from the stored blood. Tumor growth was then monitored by measuring urinary beta-hCG. All mice were killed on day 15, and the tumor weight and volume were measured.
Results: Transfusion of all allogeneic blood products enhanced tumor growth, as did the stored syngeneic whole blood. Neither fresh syngeneic blood nor the supernatant from stored syngeneic blood promoted tumor growth. Although the tumors were not visually detectable until day 10 after inoculation, by day 7 the levels of urinary beta-hCG were significantly higher in the mice that received allogeneic blood supernatant than in the mice that received saline.
Conclusions: A soluble alloantigen enhances solid tumor growth, as does an insoluble factor present in stored syngeneic whole blood. The immunomodulation associated with this factor begins to enhance tumor growth within 7 days after transfusion.