Effects of bile salts and aliphatic ionic surfactants on human lymphocyte proliferation

Background The molecular mechanisms involved in the immunosuppressive prope rties of bile salts are partly unknown. Methods The aim of the study was to compare the effects of bile salts to th ose of various compounds with a steroid structure, or straight-chain hydroc arbons of different lengths and polar groups in the human mixed lymphocyte reaction. Results We showed a significant correlation between the effects of bile sal ts and a low critical micellar concentration, a high surface activity index , and the absence of conjugation. In addition to mixed lymphocyte reaction (MLR) inhibition, chenodeoxycholate (CDC) inhibit ConA-induced IL2 producti on without any effect on IL2 R expression. Fusidate, a negatively charged s teroid, with physical properties comparable to those of deoxycholate, had s imilar effects. Cetyltrimethylammonium bromide (CTAB), which exhibited a ve ry low critical micellar concentration, inhibited mixed lymphocyte reaction in an extent comparable to cyclosporin A. In contrast, aliphatic compounds with critical micellar concentrations in the same range as bile salts but with a lower molecular area had no effect. Conclusion Amphiphilic negatively charged molecules inhibit T-cell prolifer ation to an extent that is dependent upon their hydrophobicity. These resul ts may be explained, at least in part, by a modification in the cell membra ne lipid bilayer structure.