Fibronectin and lymphocytes in inflammatory tissue. Studies of blood and synovial fluid lymphocytes from patients with rheumatoid arthritis and other inflammatory arthritides.

Abstract

Lymphocytes infiltrating tissues under chronic inflammatory conditions are often surrounded by deposits of fibronectin. We have studied the possibility that this reflects capacity of lymphocytes to synthesize fibronectin and compared lymphocytes from blood and synovial fluid with respect to fibronectin interactions. In vitro activated blood lymphocytes exhibited synthesis of a fibronectin-like molecule. Synovial fluid cells appeared to synthesize the same high molecular weight component spontaneously. Activated blood lymphocytes have cell surface fibronectin and surface components of lower molecular weight which could be immunoprecipitated with anti-fibronectin antibodies as well as by insolubilized collagen. Synovial fluid cells showed cell surface fibronectin as revealed by immunocytochemical detection but seemed to lack or have relatively small amounts of the low-molecular weight fibronectin-like surface components. Synovial fluid T cells from arthritis patients showed adhesion to fibronectin. Immunocytochemistry demonstrated presence of alpha 4 and alpha 5 beta 1 integrins at the surface of the synovial fluid T cells and RGD and LDV peptides inhibited adhesion of the cells to fibronectin. Noteworthy, a portion of synovial fluid cells with lymphocyte markers also bound to plastic. Blood lymphocytes from the same arthritis patients displayed relatively poor or negligible adhesion to fibronectin unless activated to blast transformation and did not attach to plastic. Taken together these results suggest that activated lymphocytes from blood and synovial fluid may use fibronectin of exogenous or endogenous origin when interacting with tissues during inflammatory processes. Furthermore, the presence at the lymphocyte surface of components of different molecular weight precipitated by anti-fibronectin antibodies suggests that fibronectin or its fragments can bind to the lymphocyte surface.