Fibronectin in pemphigus

In the skin organ culture model of pemphigus, fibronectin concentrations of 300 and 500 micrograms/ml inhibited pemphigus plasma-induced acantholysis and intraepidermal binding of the pemphigus antibodies examined by direct immunofluorescence. A direct interaction of fibronectin with pemphigus antibodies could not be demonstrated by chromatography of pemphigus plasma on immobilized fibronectin or by incubation with fibronectin and subsequent precipitation with antifibronectin. We then measured fibronectin concentrations in the plasma of 15 patients suffering from various types of pemphigus and presenting different activities of their disease. Immunoreactive fibronectin levels in untreated patients with active disease were generally in the low normal or even clearly in the subnormal range. They had the tendency to decrease when the disease subsided during therapy with high doses of glucocorticoids, sometimes in combination with azathioprine. The fibronectin concentration in the blister fluid of a patient with acute, untreated pemphigus vulgaris was similar to that in a plasma sample taken at the same time. Skin biopsies of pemphigus patients exhibited an essentially normal fibronectin pattern in direct immunofluorescence. We discuss a possible protective role of fibronectin in pemphigus e.g., by reducing the permeability for pemphigus antibodies in the dermal-epidermal junction zone.