Systemic immune response after rectocolonic administration of ovalbumin in mice

The aim of our study was to determine the effect of a rectocolonic preimmunization with ovalbumin on the systemic immune response induced by a subsequent subcutaneous injection of this antigen in Balb/c mice. One rectocolonic, but not intragastric, administration of 25 mg of ovalbumin induced a detectable increase in serum anti-ovalbumin antibody level. The level reached was however much lower than after subcutaneous injection. Both intragastric and rectocolonic immunization with ovalbumin induced specific systemic cellular tolerance. However, after rectocolonic, but not intragastric, preimmunization there was no systemic humoral tolerance to this antigen. These differences in systemic immune responses after rectocolonic or intragastric administration of ovalbumin could be due to different stimulation of the systemic immune system or to differences between the colonic and small bowel mucosal immune system, which remain to be elucidated.