The physiological interferon (IFN) response involves the production of little amounts of IFN in localized lymphoid microenvironments upon induction of exogenous and endogenous inducers. The aim of this work was to demonstrate whether dietary antigens and/or alimentary lectins could induce IFN in vivo after intraduodenal administration in rabbits. For this purpose we have collected simultaneously the abdominal lymph and plasma during the experiments for about 12 hours. The results show that while both onion' (Allium cepa) and cucumber' (Cucumis sativum) homogenates are ineffective, the hydrolysate of the latter induces a marked increase of IFN in the lymph suggesting that preliminary digestion (and probably gastric digestion) is crucial for the activation of IFN inducers. The maximum IFN activity occurs 7 hours after the administration and there is no concomitant activity in the plasma. Addition of bile salts to either the homogenates or the hydrolysates in unable to modify the pattern of the response. Preliminary characterization of the IFN activity has shown it to be trypsin-sensitive acid- and heat-stable and species-specific
