Reduced passage of alpha 2-macroglobulin into malignant serous effusions and diminished antifibrinolytic potential of the fluid.

The ratio of the relative concentrations of large and small proteins between effusions and serum was measured in patients with benign and malignant effusions. The ratio of values for a large protein, alpha 2 macroglobulin (alpha 2 M) was significantly (p less than 0.0005) lower in the 22 patients with tumoral effusion (0.436 +/- 0.016) and in the 16 patients with transudates (0.388 +/- 0.017) than in the 21 cases with inflammatory exudates (0.838 +/- 0.036) while the ratios between relative concentrations of the lower molecular weight alpha 1 antitrypsin (alpha 1AT) in serous fluids and sera were similar (close to 1.0) in all the above mentioned conditions. Most inflammatory exudates inhibited fibrinolysis in a urokinase activated system, while the activity of the inhibitors of fibrinolysis was very weak in tumoral effusions and in transudates. These findings suggest a rather selective passage of plasma proteins into a tumoral effusion, a fact that might be relevant for a pathogenic diagnosis.