Human monocytes produce monocyte chemoattractant protein 1 (MCP-1) in response to a synthetic peptide derived from C-reactive protein.

We reported previously that a synthetic peptide (RS-83277) derived from human C-reactive protein (CRP) augmented human monocyte/macrophage tumoricidal activity and cytokine production. RS-83287, a synthetic peptide derived from a different CRP site, was ineffective. Because chemoattractant properties have been attributed to some CRP-derived peptides, we hypothesized that RS-83277, in addition to activating effects, might promote human monocyte chemotaxis. Results indicated that neither CRP peptide RS-83277 nor RS-83287 was, itself, a chemoattractant. RS-83277, but not RS-83287, however, elicited time-dependent production of monocyte chemoattractant activity in conditioned media (CM) of cultured human mononuclear leukocytes and purified, adherent monocytes (MO). CM from nonadherent MO contained no activity, indicating that adherence was required for monocyte response. Monocyte chemoattractant activity was dose-dependent and was removed by treatment with immobilized antibody to human monocyte chemoattractant protein 1 (MCP-1) but not by irrelevant IgG. These results indicate that a specific peptide segment of CRP acts upon human adherent monocytes to promote production of the autocrine chemotactic and activating factor MCP-1. Data suggest that degraded CRP represents a complex source of biologically active peptides which, among other effects, may amplify monocyte recruitment to sites of injury.