Studies on relationship between serum properdin and cancer II. Studies on the serum properdin levels of tumor bearing animals and patients with malignant tumors

1. The properdin levels in sera from mice bearing Ehrlich ascitic carcinoma and from rabbits with Brown-Pearce carcinoma decrease inversely with the increase of the ascites or the tumors. In the incipient period of tumor transplantation, the level rather rises. When the tumor is proliferating or large, the level keeps falling or is low. On the contrary, when the tumor is regressing or disappears, the level elevates or reverts to that before transplantation. Strong A and R III mice with spontaneous mammary cancer have markedly low serum properdin levels as compared with those of healthy mice. 2. The properdin levels are less than 2 units per milliliter of the serum in 44.4 per cent of patients with gastric cancer, in 18.2 per cent of ones with non-malignant tumor and in 18.2 per cent of ones with gastric or duodenal ulcer. The abnormal low level has been found in 33.3 per cent of patients without recurrence, who had undergone extended radical gastrectomy combined with radical lymphadenectomy for gastric cancer. 3. Some correlation can be seen between the serum properdin levels and the degree of progress of gastric cancer. 4. The cancer patients with low total serum protein have lower serum properdin levels than those having nomal protein. 5. As for influence of surgical operation on the serum properdin levels, there is observed a tendency that a minor operation causes the levels to increase and a major operation causes the levels to fall. 6. It has been inferred that the properdin system could be one of the host natural resistance against cancer.