HUMAN MONOCLONAL-ANTIBODIES FROM STOMACH CARCINOMA PATIENTS REACT WITH HELICOBACTER-PYLORI AND STIMULATE STOMACH-CANCER CELLS IN-VITRO

Background. In recent studies, an increased incidence of gastric adeno carcinomas was observed in patients with Helicobacter pylori infection . However, the extent to which this coincidence is caused by immunolog ic mechanisms is unknown. Methods. Two human monoclonal antibodies (Mo Abs) from patients with stomach carcinoma and H. pylori-associated gas tritis were isolated and established by fusion of spleen cells with th e heteromyeloma HAB-1. The reactivity of these human MoAbs was investi gated in functional adhesion assays and on Western blots of tissue, tu mor cell, and bacterial extracts. Their stimulation and proliferation were tested by the MTT test and 3-H-thymidine incorporation tests. Res ults. The two monoclonal immunoglobulin-M antibodies, 103/51 and 105/7 9, inhibited adhesion of tumor cells. On bacterial extracts antibody 1 03/51 identified protein bands of 55 kilodaltons (kd) and 80 kd, and i n tumor cell extracts, a specific protein of approximately about 110 k d and 140 kd. Antibody 105/79 identified a 55 kd protein in bacterial extracts and a 110 kd protein in tumor extracts. In addition, in the 3 -H-thymidine incorporation and MTT assay the antibodies showed a stimu latory and growth-enhancing effect on tumor cells in vitro. A similar activity was observed in sera from patients with gastric carcinoma, in dicating a physiologic role of such antibodies in vivo.