Background:The capacity to generate (interferon-gamma) IFN-γ, a potent immunoregulatory and inflammatory cytokine, is low in neonates and deficient in patients with food allergy.Methods:We investigated the effect of IFN-γ on antigen transport in the gut. In experiment I rat pups were randomized into two groups at the age of 14 days i.e., before gut maturation: Group IFN was given intraperitoneally recombinant rat IFN-γ on days 14, 16, 18, 20. In experiment II, rats were randomized into two groups at the age of 26 days, i.e., after gut maturation: Group IFN received the IFN-γ treatment on days 26, 28, 30, 32. Controls in both experiments received sterile saline. The absorption of horseradish peroxidase (HRP) across jejunal segments with and without Peyer's patches was studied in Ussing chambers on days 21 and 33 for experiments I and II, respectively.Results:In experiment I, the absorption of intact HRP across both types of segments was significantly increased in Group IFN compared to controls. The mean (95% confidence interval) rate of degraded HRP absorption across patch-containing segments in Group IFN was significantly greater than in controls, 4420 (3162-6179) ng · h-1· cm-2in comparison to 1550 (633-3790) ng · h-1· cm-2; F = 8.96, p = 0.009.Conclusion:IFN-γ increases macromolecular transport before gut maturation particularly across Peyer's patches. This Peyer's patch-targeted effect can be important eliciting mucosal immune responses against dietary antigens early in life and aiding their immune exclusion.