Fig. 4. Erythrocyte (RBC) cell volume, but not leukocyte number, determines the metastasis promoting effects of the transfusion. ( A ) Numbers (mean ± SEM) of leukocytes per a transfusion containing 0, 0.75, 1.5, or 2.25 ml RBCs (diluted in saline to a standard 3-ml volume). Transfusions were conducted after 14-day storage of leukoreduced or nonleukoreduced packed cells. Notice that the two groups contrasted by the horizontal bar have similar numbers of leukocytes but different RBC volumes. ( B ) Percentage of MADB106 lung tumor retention (mean ± SEM) in the different groups. Notice that the same two groups contrasted are significantly different from each other in tumor retention (**, protected least significant difference, P < 0.05), although they have the same number of leukocytes ( A ). * Significant pairwise difference from the respective saline control group (protected least significant difference, P < 0.05). n = 67; 6–10 per group.