Effect of oral antigen and antibody exposure at birth on subsequent immune status. A study in neonatal pigs.

Background: The purpose of this work was to investigate the effects of early low-level exposure to either antigen or antibody alone on subsequent immune responses in entirely immunologically naïve animals. This is impossible in species with a permeable placenta such as rodents or humans, where both antigen and antibody can be transferred in utero. It is, however, possible in pigs, due to the impermeable placenta of the sow. Thus, neonatal piglets were used for this study.

Methods: Newborn piglets were exposed to ovalbumin (OVA) at dosages similar to those used in rodents to sensitise, as well as to serum containing anti-OVA antibodies.

Results: Both single low doses of OVA (10 and 1,000 mg per animal) induced classical oral tolerance following a systemic challenge: both doses reduced specific systemic IgG responses and tertiary in vitro recall proliferative responses by splenocytes and especially by mesenteric lymph node (MLN) cells. Additionally, dietary challenge had phenotypic effects on helper T cells in MLN, which could be reversed by OVA at birth. In contrast, giving antibody as serum collected from hyperimmune or orally tolerant pigs had no functional effects.

Conclusions: Overall, our data support the hypothesis that contrary to previous work in rodents, very early exposure of neonatal pigs to a single small dose of antigen can reduce subsequent immune responses. This may have implications for human health. However, although these data point to a reducing/regulatory effect of low doses of antigen in very young animals, they cannot be extrapolated directly to allergy.