Covalent coupling of palmitate to ovalbumin inhibits and blocks the induction of oral tolerance.

Oral tolerance is a phenomenon that may occur in animals exposed to soluble antigens for the first time by the oral route. In the present study, we show that oral tolerance against ovalbumin (Ova) can be obtained after intragastric administration of the antigen in the presence of free residues of palmitate. On the other hand, oral tolerance induction is blocked when the residues of palmitate are covalently bound to the antigen (Ova-palmitate conjugates). We have also noticed that oral administration of Ova-palmitate conjugates can boost and/or prime experimental animals for Ova-specific cellular and humoral systemic immune responses. Oral treatment with the conjugates also induces the production of local secretory immunoglobulin A (IgA) as measured in intestinal washes. Furthermore, Ova-palmitate given orally can inhibit oral tolerance induction by naïve Ova.