Beta 1 (CD29) integrin expression in rheumatoid synovial membranes: an immunohistologic study of distribution patterns.

Cellular attachment to, and migration into, tissues are critical aspects of the inflammatory process. Our studies were undertaken to examine the distribution of one of the families of adhesion molecules, the beta 1 integrins (VLA antigens), in inflamed rheumatoid synovial tissues. The distribution of lymphocyte subsets and the beta 1 integrins (beta 1, VLA-1, 2, 3, 4, 5) were studied in 10 rheumatoid synovial membranes using immunohistochemistry and monoclonal antibodies. The majority of lymphocytes stained positively for beta 1, VLA-3, VLA-4 and VLA-5. Intravascular mononuclear cells adherent to the endothelium appeared to generally express low levels of beta 1 when compared to those in the extravascular space, suggesting that lymphocytes may augment their expression of this molecule subsequent to their extravasation into the tissue. Cells in the synovial lining layer expressed beta 1, VLA-1, VLA-3 and and VLA-5. The endothelium of the synovial vasculature stained intensely for beta 1, VLA-1, VLA-3 and VLA-5 with more limited staining for VLA-2. The venules and capillaries in and around the subsynovial lymphocytic aggregates demonstrated the most intense vascular staining. We conclude that the beta 1 integrins are expressed by a variety of cells in the rheumatoid synovial membrane. The expression of beta 1 integrins may be subject to regulation by the inflammatory microenvironment thus contributing to a more adhesive environment into which inflammatory cells are more readily recruited and retained.