IL-10 enhances CCL2 release and chemotaxis induced by CCL16 in human monocytes

CCL16 is a CC chemokine originally identified as a liver-expressed chemokine. Its expression has been detected in activated monocytes where it is up-regulated by stimulation with IL-10. This is in contrast with IL-10's inhibition of the expression of most chemokines. CCL16 is chemotactic for monocytes, lymphocyte and dendritic cells. We investigated whether CCL16 displays biological activities other than chemotaxis and whether IL-10 affects monocyte response to CCL16. We show that CCL16 induces the expression of CCL2 at the mRNA and protein level, but does not affect that of CCL5, CCL18 and proinflammatory cytokines. This effect was prevented by treatment with pertussis toxin and may thus be mediated by G-protein-coupled receptors. IL-10 markedly increased CCL2 production induced by CCL16, but suppressed that of CXCL8. It also enhanced the chemotactic response to CCL16. Addition of antibodies blocking CCR1, but not CCR8, prevented this enhanced chemotactic response and suggested that CCR1 is primarily involved. We propose that IL-10 modulates the effects of CCL16 on monocytes by increasing their CCR1-dependent response. The coordinated secretion of CCL16 and IL-10 may thus enhance monocyte infiltration.