THE INTERLEUKIN-8 RECEPTOR-B AND CXC CHEMOKINES CAN MEDIATE TRANSENDOTHELIAL MIGRATION OF HUMAN SKIN HOMING T-CELLS

We studied the involvement of chemokines that bind to G protein-couple d receptors in the migration of skin homing T cells across a bilayer v ascular construct (BVC) consisting of a fibroblast matrix underneath a n activated endothelial (EC) monolayer. Based on the expression of the cutaneous lymphocyte-associated antigen (CLA). a skin homing receptor , CD45R0(+) T cells freshly isolated from blood or HUT-78 cutaneous T lymphoma cells were separated into CLA(+) and CLA(-) subpopulations. T hese T cells were incubated on interleukin (IL)-1 beta and tumor necro sis factor-alpha-activated EC, and the number of transmigrated cells w as determined. The chemokine IL-8 was selectively involved in the enha nced migration of CLA(+) T cells across activated EC as demonstrated b y blocking antibody to IL-8 but not to GRO-alpha, MCP-1 and RANTES. Id entical results were obtained with both human umbilical vein EC (HUVEC ) and microvascular skin EC (HDMEC). Pertussis toxin selectively inhib ited the enhanced transendothelial migration (TEM) of CLA(+) T cells, suggesting that CLA-dependent TEM depends on Gi protein-transmitted si gnals. Moreover, the IL-8 receptor B (IL-8RB) appeared to be functiona lly involved in TEM, as demonstrated by receptor desensitization with the CXC chemokines IL-8 and GRO-alpha and by blocking the IL-8RB with specific monoclonal antibodies. Although only the IL-8RB was involved in CLA-dependent TEM, mRNA encoding IL-8RA and IL-8RB was expressed by both CLA(+) and CLA(-) T cells. This correlated with IL-8RA and IL-8R B surface expression on these cells. Thus, the IL-8RB is selectively f unctional in TEM of T cells expressing the skin homing receptor CLA. O ur results demonstrate a critical role for IL-8 and possibly other IL- 8RB ligands in addition to the IL-8RB in TEM and suggest the involveme nt of these molecules in the homing of specific T cells to inflamed sk in.