Lymphocyte-endothelial interactions in inflamed synovia: involvement of several adhesion molecules and integrin epitopes.

The role of several adhesion molecules for lymphocyte-endothelial interactions in the synovia of rheumatoid arthritis patients was studied using the frozen section assay. Partial inhibition of lymphocyte binding to endothelium of synovial sections could be observed with antibodies against CD44, L-selectin, and beta 1- and beta 2-integrins, pointing to the participation of several adhesion molecules in the regulation of lymphocyte immigration into inflamed synovia rather than the presence of a unique homing receptor. Different degrees of inhibition were found within a series of antibodies against alpha 4- and beta 1-integrins known to have functional effects in other interaction systems. In addition, increased binding to endothelial cells was induced when lymphocytes were pretreated with TS2/16 anti-beta 1 IgG, whereas binding to non-endothelial components of synovia was increased after treatment with HP 2/4 (anti-alpha 4) Fab. The data suggest a multifunctional role of alpha 4/beta 1-integrins in directly mediating adhesion as well as regulating adhesive interactions in the rheumatoid synovia.