Anti-T antibodies and peanut-agglutinin-binding glycoproteins in sera of patients with gastric cancer

Agglutinating antibodies to neuraminidase-treated red blood cells (anti- T agglutinins) are known to be reduced in patients with gastric cancer. The antigenic determinant of anti-T agglutinin is known to have a disaccharide structure [Gal(β1-3)GalNAc], the same specificity as peanut agglutinin (PNA). We examined sera of 27 patients with gastric cancer and 30 controls for anti-T agglutinins, anti-T antibodies and PNA-binding glycoproteins. Anti-T agglutinins were titrated by a microtiter hemagglutination method. Levels of anti-T antibodies were determined by enzyme immunoassay using synthetic glycoconjugate [Gal(β1-3)GalNAc O-α-linked to human serum albumin] as an antigen. Levels of PNA-binding glycoproteins in sera were measured by sandwich enzyme-linked lectin assay using wheat germ agglutinin and peroxidase-conjugated PNA. Titers of anti-T agglutinins were significantly lower in patients with gastric cancer than in controls (P = 0.041). Levels of anti-T antibodies were not significantly different in patients with gastric cancer and controls; however, decreased levels of anti- T antibodies were more frequent in patients with gastric cancer than in controls (P = 0.001). Levels of PNA-binding glycoproteins were significantly higher in sera of patients with gastric cancer than in controls (P = 0.001). The levels of anti-T antibodies inversely correlated with the levels of PNA- binding glycoproteins in sera of patients with gastric cancer (r = -0.44, P = 0.021). These results suggest that the decrease in anti-T antibodies in sera of patients with gastric cancer might be due to immune complex formation between circulating PNA-binding glycoproteins and anti-T antibodies.