Dietary nucleic acids promote a shift in Th1/Th2 balance toward Th1-dominant immunity

Background Dietary sources of nucleic acids and their relative components a re known to affect host immune function; however, it has not yet been clari fied whether such dietary nucleic acids influence the pathogenesis of aller gic reaction. Objective The purpose of this study is to elucidate the effect of dietary n ucleic acids on Th1/Th2 balance. Methods Both human flora-associated and specific pathogen-free BALB/c mice were maintained on either nucleic acid-free, or -supplemented diets. The ef fects of nucleic acids on both in vivo antibody levels and in vitro splenoc yte cytokine production were compared using these mice. Results Supplementation of nucleic acids caused a reduction in the serum an tibody levels of total IgM, IgG, IgG1, and IgE in the human flora-associate d mice without affecting the composition of intestinal flora. In contrast, there was no significant difference of the serum IgG2a levels between nucle ic acid-free and -supplemented mice. Such a phenomenon as that, the supplem entation of dietary nucleic acids reduces the serum IgE or IgG1 levels, but not the IgG2a level, was also seen in the specific pathogen free mice. Mor eover, when the mice were systematically challenged with ovalbumin, the sup plementation of nucleic acids also suppressed the serum ovalbumin-specific IgE and IgG1 antibody levels as well as in vitro IL-4 and IL-10 secretion, while enhancing both the serum ovalbumin-specific IgG2a antibody levels and in vitro IFN gamma secretion. Conclusion These results suggested that dietary nucleic acids may play an i mportant role in promoting a shift in Th1/Th2 balance toward Th1-dominant i mmunity.