Monocytes lose their mitogenic potency as they interact with ECs. (A) Primary monocytes added to subconfluent HUVECs (solid line) were removed at different time points and placed over new subconfluent HUVECs (broken line). The potentiated proliferation was measured as ³H-thymidine incorporation 20 hours after the addition of monocytes. (B) mRNA levels of TNFα in untreated monocytes and monocytes separated from monocyte-HUVEC coculture, standardized to GADPH mRNA. (C) mRNA levels of IL-1β in untreated monocytes and monocytes separated from monocyte-HUVEC coculture, standardized to GADPH mRNA (n ≥ 3, *P < .001).