[The role of fibronectin in nonspecific defense from the immunologic viewpoint]

The present article gives a review of the essential data of literature concerning the importance of fibronectin (Fn) for the unspecific defence. In this case the function of Fn postulated as unspecific opsonin stands in the foreground. Fn mediates the binding of gelatine particles, bacteria and other above all particular materials on phagocytizing cells (monocytes, macrophages and neutrophils). Up to now it is, however, controversial whether or not this binding causes an increased endocytosis. The participation of cofactors or inhibitors and the problem whether Fn or certain proteolytic Fn-fragments are effective still need a further clarification. Fn, its fragments or Fn-substrate-complexes can activate phagocytes and have a chemotactic effect on them. The mechanism of activation is still unknown, for monocytes in increased expression of Fc- and C3b-receptors is supposed. Fn might consequently perform a defence function as an unspecific cell activator and at the same time have a pro-inflammatory influence. There are controversial opinions as to the questions which phagocytes are activated and which Fn-molecules (complete plasma-Fn or fragments) are responsible. The high sensitiveness of Fn to proteolytic enzymes and denaturating processes is supposed to be one of the causes for the different results.