Fibronectin and deposits of fibrinolytic components in glomerular capillary walls

The distribution of fibronectin (FN) and the depositions of fibrinolytic components in human renal glomeruli with a variety of pathologic disorders were examined on biopsy specimens by immunofluorescence and immunoenzymatic methods. In a majority of the cases with thickening of capillary walls and/or with fibrin deposits in the capillary walls, staining for FN along the walls of the capillary loops (capillary pattern) was noted in addition to the staining in the mesangial area. In the capillary pattern with fibrin deposition, deposits of alpha 2-plasmin inhibitor and plasminogen, which are major components of the fibrinolytic system, were also seen along the capillary walls with a high frequency of occurrence. Plasminogen deposits, however, were found only in the glomeruli with deposits of alpha 2-plasmin inhibitor. There was no direct relationship between the degree of proteinuria and the appearance of the capillary pattern of FN or the deposition of the fibrinolytic components. These findings suggest that the appearance of FN in the walls of the capillary loops has some causal relationship with the local activation of blood coagulation factors which is frequently followed by activation of the fibrinolytic enzyme system.