The mRNA expression levels of AML-1A, AML-1B, MIP-1α, and IL-3 in bone marrow samples from patients with MM and healthy donors. Relative mRNA expression levels of AML-1A, AML-1B, MIP-1α, and IL-3 were determined by RT-PCR analysis. (A) (B) Total bone marrow mononuclear cells (A) and CD138⁺ purified plasma cells (B) from healthy donors and MM patients were examined. The mRNA expression levels of MIP-1α and IL-3 were significantly enhanced in total bone marrow samples (A) as well as purified plasma cells (B) from patients with MM as compared with healthy donors. IL-3 expression levels in purified plasma cells from patients with MM correlated with enhanced MIP-1α and decreased AML-1B expression (r = 0.753 for IL-3 versus MIP-1α; r = 0.62 for IL-3 versus AML-1A). (C) IL-3 protein expression levels in bone marrow plasma from MM patients and healthy donors were measured by commercial ELISA kits. Expression levels of IL-3 were significantly increased in 12 of 16 bone marrow plasma samples from MM patients as compared with healthy donors.