IL-6 ACTS ON ENDOTHELIAL-CELLS TO PREFERENTIALLY INCREASE THEIR ADHERENCE FOR LYMPHOCYTES

Using a quantitative monolayer adhesion assay, the current report show s that treatment of human umbilical vein endothelial cells (HUVEC) wit h IL-6 increases their adhesiveness for blood lymphocytes, particularl y CD4(+) cells, but not for polymorphonuclear cells and monocytes. Thi s effect, which was most pronounced when using low concentrations of t he cytokine (0.1-1.0 U//ml) and a short incubation period (4 h), was a lso apparent with microvascular endothelial cells and a hybrid endothe lial cell line. Skin lesions from patients with mycosis fungoides cont ain high levels of IL-6, and blood lymphocytes from patients with this disorder also exhibited an enhanced adhesion to IL-6-treated HUVEC. T he cytokine enhanced intercellular adhesion molecule-1 (ICAM-1) expres sion and induced the expression of vascular cell adhesion molecule-1 ( VCAM-1) and E-selectin on endothelial cells. Antibody blocking studies demonstrated that the vascular adhesion molecules ICAM-1, VCAM-1 and E-selectin and the leucocyte integrin LFA-1 all contributed to lymphoc yte binding to endothelium activated by IL-6. It is proposed that IL-6 may be involved in the recruitment of lymphocytes into non-lymphoid t issue.