Gastrointestinal neuropeptides suppress human colonic lamina propria lymphocyte DNA synthesis.

Gastrointestinal neuropeptides have been shown to modulate the circulatory immune system, but their effect on the mucosal immune system is not well defined. We studied the effect of VIP, SOM, S-P and Bomb on thymidine incorporation into human colonic lamina propria lymphocyte (LPL) DNA. Physiologic concentrations of VIP, SOM, S-P and Bomb significantly suppressed thymidine incorporation into Con A-stimulated human LPL. These neuropeptides did not affect DNA synthesis when LPL were induced with phorbol ester (PDB) and calcium ionophore (ionomycin). Our data suggest that a) VIP, SOM, S-P, and Bomb may have a regulatory role in the human mucosal immune system, and b) Bomb should be added to the list of neuropeptides which affect the gut immune system.