Adhesion of colony-forming units to immobilized PF4 requires metabolic activity. (A) Marrow mononuclear cells were plated in wells coated with bovine serum albumin (BSA), poly-L-lysine (PLL), or PF4 in 37°C or 4°C; then adherent and nonadherent cells were separated and cultured in methylcellulose for 21 days. Total colony-forming units (BFU-E, CFU-GM, and CFU-GEMM) were enumerated. (B) Marrow mononuclear cells were plated in wells with immobilized PF4 in culture medium without (Control) or in the presence of 0.1% NaNO₃ and 2-deoxyglucose (NaN₃/2-DOG). Adherent and nonadherent cells were separated and cultured in methylcellulose for 21 days. Colonies forming units were enumerated. E indicates burst forming units–erythrocytes; GM, colony-forming units–granulocytes macrophages; and GEMM, colony-forming units–granulocytes erythrocytes, macrophages, and megakaryocytes. Error bars represent SEMs.