Occurrence of soluble supra-molecular FN-fibrin complexes in the plasma of children with recurrent respiratory infection.

Objectives Fibronectin (FN) is able to bind fibrin and FN-fibrin complexes and is found in the plasma of some patients suffering from inflammatory disease. The present study was undertaken to determine whether soluble supra-molecular FN-fibrin complexes were present in the plasma of children with recurrent respiratory infections (RRI). Design and methods The frequency of occurrence and relative amounts of the supra-molecular FN-fibrin forms, concentrations of immunoglobulins and numbers of natural killer cells (NK) were determined in the plasma of children with recurrent respiratory infections. The frequencies of these parameters were compared with their frequencies in the plasma of children with acute respiratory infections and plasma from healthy children. Results SDS-agarose immunoblotting of patients' plasma revealed the presence of several additional FN-fibrin bands, with decreasing electrophoretic mobilities and increasing molecular masses of 750kDa, 1000kDa, 1300kDa, 1600kDa and 1900kDa. Such FN-fibrin complexes occurred with higher frequency and in larger amounts in the plasma of children with RRI and acute infection than they did in plasma from normal children. Moreover, bands above 1000kDa were absent in most young healthy individuals. The occurrence of FN-fibrin complexes did not correlate with either immunoglobulin concentrations, or with the number of NK cells. Conclusions The occurrence of plasma supra-molecular FN-fibrin complexes is associated with acute and recurrent respiratory infections of children.