Orally administered lead chloride induces bias of mucosal immunity

The hypothesis that lead disturbs gut immune functions upon oral ingestion was tested. Long-term exposure to oral PbCl2 for 10 days caused persistent downregulation of TGF-beta mRNA levels in intestinal tissue. PbCl2 also dis turbed oral tolerance induction to the dietary antigen ovalbumin, Upon chal lenge with an immunizing dose of ovalbumin and rechallenge of draining lymp h node cells in vitro, tolerance induction was partially suppressed in anim als exposed to oral PbCl2. This was shown by increased proliferation to ant igenic stimulus, increased production of IFN-gamma and decreased secretion of TGF-beta. In conclusion, we show for the first time that oral exposure t o PbCl2 has a significant effect on the gut immune system, demonstrated by a bias of the cytokine pattern towards Th, and by disturbed oral tolerance mechanisms. (C) 2000 Academic Press.