Increased expression of VLA-5 adhesion molecules on synovial fluid T lymphocytes in chronic polyarthritis: a consequence of T-cell activation.

This study focuses on the consequences of T-lymphocyte activation in chronic polyarthritis in terms of expression of cell surface receptors interacting with extracellular matrix (ECM). The expression of the VLA group of integrins was studied on in vitro-stimulated peripheral-blood T cells, and on peripheral-blood and synovial-fluid mononuclear cells (MNC) of patients with polyarthritis. The VLA expression was measured by flow cytometry using monoclonal antibodies (MoAbs) against alpha-subunits of the VLA family. VLA-alpha 4 and VLA-alpha 5, but not VLA-alpha 1, were expressed on a major fraction of unstimulated peripheral-blood T cells both in the patients with polyarthritis and in healthy individuals. Two distinct populations, VLA-alpha 5-high and VLA-alpha 5-low, were found in resting peripheral-blood T lymphocytes. Two days after stimulation by phorbol 12-myristate 13-acetate (PMA) and concanavalin A, most T cells became VLA-alpha 5-high. In patients with chronic polyarthritis, the expression of VLA-alpha 1 and VLA-alpha 5 was always higher on synovial-fluid T cells than on peripheral-blood T cells. These results give further support to the hypothesis that upon activation the induction of the VLA adhesion-molecule expression may be a factor contributing to the accumulation of T cells in the inflamed synovium.