IL-10 INHIBITS THE ADHESION OF LEUKOCYTIC CELLS TO IL-1-ACTIVATED HUMAN ENDOTHELIAL-CELLS

Cytokines play an important role in the recruitment of leukocytes from blood to sites of tissue injury and inflammation. Previous studies showed that the pro-inflammatory cytokine, IL-1, induces the adhesion of leukocytes by up-regulating the expression of the adhesion molecules ICAM-1 and VCAM-1 on endothelial cells. IL-10, a pleiotropic mediator, inhibits the production of cytokines by macrophages and down-regulates the antigen-presenting function of macrophages, thereby acting as a suppressor of immune responses. This study was undertaken to evaluate the effect of IL-10 on the adhesion of leukocytic cells to human umbilical vein endothelial cells. IL-10 inhibited the adhesion of a human monocytic cell line (THP-1) and a human lymphoblastic T-cell line (MOLT-4) to IL-1-stimulated endothelial cells. IL-10 also down-regulated the expression of ICAM-1 and VCAM-1 on IL-1-activated endothelial cells. IL-10-treated THP-1 cells adhered less than untreated THP-1 cells to IL-1-activated endothelial cells, whereas direct treatment of MOLT-4 had minimal effect on its adhesion to cytokine-activated endothelial cells. These results suggest that IL-10 counteracts the pro-inflammatory effects of IL-1 and regulates the adhesion of leukocytic cells to endothelial cells.