Modulation of human colonic lamina propria lymphocyte proliferation. Effect of bile acids and oxidized fatty acids.

Bile acids were been implicated in several pathologic processes, such as secretory diarrhea, carcinogenesis, and immunomodulation of human peripheral blood lymphocytes. Nevertheless, their effect on the human gut immune system is not known. In this study we investigate the effect of several bile acids (cholate, deoxycholate, chenodeoxycholate) and 13-hydroperoxylinoleic acid (conc. 0.1-1000, microM) on human colonic lamina propria lymphocyte (LPL) DNA synthesis and cell proliferation. In addition, the effect of these bile acids on LPL ornithine decarboxylase activity was also determined. Significant dose-dependent inhibition of [3H]thymidine incorporation in Con A-stimulated LPL was observed. Parallel inhibition was seen on LPL cell proliferation. Furthermore, bile acids inhibited ornithine decarboxylase activity in Con A-stimulated LPL. These effects on cell proliferation were not due to the LPL cytolysis as viability and cell membrane integrity were not altered. Our results suggest that bile acid has an immunoregulatory function on the human mucosal immune system and may have a role during pathological states.