Inhibition of Immunoglobulin Production in Human Namalwa Cells and Rat Spleen Lymphocytes by Bile Acid

Abstract

The effects of bile acids on the proliferation and IgM production of human lymphoblastoid Namalwa cells and on the Ig production of rat spleen lymphocytes were examined. Among the free bile acids examined, two dihydroxy bile acids, CDCA and DCA, inhibited the proliferation of Namalwa cells and Ig production by rat spleen lymphocytes at concentrations above 20 μg/ml, while the inhibitory effect of a trihydroxy bile acid, CA, was much weaker. The inhibitory effects of their conjugated bile acids were weaker than those of the free ones, and the DCA derivatives were more toxic than the CA ones. These results suggest that dihydroxy bile acids were more toxic to Ig production by spleen lymphocytes than trihydroxy ones. The effect of bile acids on Ig production by the lymphocytes was examined in the presence of such mitogens as LPS, PHA, ConA, and PWM. As a result, TDCA inhibited their IgG and IgM production at 200μg/ml independently of the mitogen addition, while TCA was almost ineffective. It thus seems likely that the bile acid inhibits the Ig production by spleen lymphocytes through non-specific inhibition of the both T and B cell functions.