The effects were studied of interleukin 4 (IL-4) on T cell-synovial cell adhesion and on the expression of adhesion molecules on the surface of synovial fibroblast-like cells.
The adhesion of T cells toward the synovial cells were measured by 51chromium-labelled adhesion assay. The expression of adhesion molecules on synovial cells were analysed by flowcytometry.
Stimulation of synovial cells with IL-4 increased T cell-synovial cells adhesion in a time- and dose-dependent manner. IL-4 considerably enhanced the expression of VCAM-1 on the surface of synovial cells, but not the expression of ICAM-1 and ELAM-1. The combination of IL-1 beta and IL-4 had no effect on the expression of ICAM-1 or VCAM-1 on the surface of synovial cells. The increased adhesion of T cells to IL-4 stimulated synovial cells was inhibited significantly by adding anti-VCAM-1 or anti-CD29 monoclonal antibody. Furthermore, anti-VLA-4 alpha or the combination of anti-VLA-4 alpha and anti-VCAM-1 antibodies blocked completely T-cell binding to IL-4 stimulated synovial cells.
These results suggest that the increased adhesion of T cells to IL-4-stimulated synovial cells is mediated by VLA-4/VCAM-1 pathway.