This calls into question the applicability to the human situation of studies performed on the lower genital tract in animal models. In addition, the observed failure of HCl to substitute for lactic acid suggests the specificity of lactic acid, and not just an acidic pH, for IL-23 induction. Thus, experimental protocols as well as commercial products that attempt to acidify the vagina with acids other than lactic acid do not mimic the natural environment and may be less than ideal. The implication that lactic acid may specifically aid Cell Cycle inhibitor in immune defense

leads one to question currently held beliefs about vaginal health. Vaginal lactic acid production by both the underlying epithelium (Gross, 1961) and endogenous lactobacilli and other bacteria contribute

to the final lactic acid concentration. Individual differences in colonizing lactobacilli and other components of the vaginal flora, variations in the genetic background that influence glucose metabolism and unique MK 2206 environmental and dietary exposures would all be expected to result in variations in lactic acid production. We postulate that the extent of lactic acid production, and not bacterial hydrogen peroxide production, is a key component of the innate immune defense mechanisms at this site. A recent investigation using gene amplification technology has revealed that the major Lactobacillus sp. in asymptomatic North American women is Lactobacillus inners, a bacterium that does not produce hydrogen peroxide (Ravel et al., 2010). Another study has demonstrated that both cervicovaginal fluid and semen block any hydrogen peroxide-induced microbicidal activity (O’Hanlon et al., 2010). Further study of larger numbers of women is clearly warranted to confirm our findings as well as to help unravel the misconceptions that now exist about vaginal bacterial flora and innate defense mechanisms

at this anatomical site. It would also be of interest to determine whether other organic acids that are structurally related to lactic acid, and that may be present in the vagina, have similar immunological Methocarbamol effects. In this regard, it has been demonstrated that lactate, but not butyrate, acetate, dichloroacetate, citrate or malate, augments lipopolysaccharide-induced IL-2 production by murine splenic T cells (Roth & Droge, 1991). In females before puberty and after menopause, vaginal lactic acid levels are much reduced and vaginal pH is elevated. Whether this contributes to a possible increased susceptibility to gram-negative bacterial infections under these conditions is not known and is worthy of investigation. In general, mucosal infection favors the induction of the Th17 subset while intravenous infection is characterized by the induction of Th1 cells (Pepper et al., 2010). This suggests that antimicrobial immunity at mucosal surfaces is preferentially geared towards IL-23 and IL-17 induction and away from the production of Th1 lymphocyte-generated IFN-γ.