Secretion of MCP-1 by monocytes/macrophages and its role in the downmodulation of MCP-1–specific binding sites. (A) Secretion of MCP-1 during monocytes differentiation. MCP-1 was measured by ELISA in the culture supernatants of freshly isolated monocytes (day 1) and 7-day–cultured macrophages. Results obtained with 3 different donors are shown. (B) Effect of antibody to MCP-1 on the specific binding of125I-MCP-1 to differentiating monocytes. Cells from 4 different donors were cultured in the presence (○) or in the absence (•) of polyclonal antibody to MCP-1 (5 μg/mL) for 1 or 7 days, extensively washed to remove the unbound antibody, and processed for binding studies as described in Fig 3. The mean percentage values (±SD) versus day 0 MCP-1 specific binding are shown. Statistical analysis showed that the differences in the binding of MCP-1 in monocytes cultured in the presence of antibody to MCP-1 were statistically significant (2-way analysis of variance P = .0194) with respect to untreated control cultures.
