The effects of dexamethasone and lenalidomide on erythropoiesis are influenced by macrophage cocultures. Macrophages were confirmed by presence CD68 by flow cytometry (A) and by immunofluorescence (B), with the green stain representing CD68 and the blue stain representing DAPI. After 3 days of treatment with the compounds in liquid culture, the amount of TNF-α in the supernatant was quantified by a chemiluminescent immunoassay (C). The experiment was performed in triplicate and repeated with similar results. After 3 days of treatment with the compounds in liquid culture, cells were plated in methylcellulose without drugs. Data are presented as the number of colonies per 3200 cells plated. The effects of dexamethasone (Dex) and lenalidomide (Len) on CFU-E colony formation are shown in panel D. The effects of Dex and Len on BFU-E colony formation are shown in panel E. The experiments were performed in triplicate and repeated with similar results. In panel C, a 2-tailed Student t test was used. **P ≤ .01; *P ≤ .05. In panels D and E, ANOVA was used and the statistical findings are discussed in the text.