[The role of monocytes in network mediated by both fibronectin and monokines in inflammation]

The effects of both fibronectin (FN) and monokines (IL-1 alpha, IL-6, TNF) on monocyte activation were studied. FN in the culture medium (200 micrograms/ml) induced strong monokine production that was mediated by the domain epitope including RGD sequence on FN and the VLA-5 integrins on monocytes. Each monokine or the combination of suboptimal dose of any monokines strongly induced FN production. These results indicate that monocytes activation in vitro may depend on not only monokines but on adhesion molecules such as FN-VLA-5. Peripheral blood monocytes from patients with systemic lupus erythematosus (SLE) demonstrated low responses to both fibronectin and monokines, while the plasma levels of FN in SLE patients elevated markedly compared with normal individuals (640 vs 285 micrograms/ml). Many studies have been reported that cytokines elevated in serum from SLE patients. These results indicated that maximally activated monocytes with both monokines and soluble FN in vivo in SLE patients could not be activated in vitro. Together with these results, FN play important roles in the cellular and humoral mechanisms of inflammation.