Digestion, Absorption and Tissue Distribution of Ovalbumin and Palmitoyl-ovalbumin: Impact on Immune Responses Triggered by Orally Administered Antigens

Previous work in this laboratory has demonstrated that ovalbumin coupled to palmitoyl residues (palmitoyl-Ova) does not induce oral tolerance. The present study sought to determine whether this coupling affects digestion, absorption and transfer of antigen. Ova and palmitoyl-Ova were shown to be digested differently in vitro by proteolytic enzymes and presented different tissue distribution kinetics after being labelled with (99m)technetium and orally administered to animals. Palmitoyl-Ova remained longer in the stomach, while native Ova was quickly transferred to the gut and other organs. After 3 h, higher levels of palmitoyl-Ova were found in the blood, Peyer's patches, mesenteric lymph nodes, liver and, especially, the spleen, which appears to be essential for immunization with palmitoyl-Ova. In fact, splenectomized mice treated orally with palmitoyl-Ova became tolerant, while tolerance to Ova was not affected. Thus, palmitoyl coupling was demonstrated to affect antigen digestion, absorption and transport. This is the first time that the spleen has been shown to be required for oral immunization with palmitoyl-Ova.

Schistosoma mansoni: human serum and release of proteins from schistosomula

Radioiodinated surface proteins of schistosomula of Schistosoma mansoni, including those involved in low density lipoprotein binding, are released into a defined culture medium at 37 C at slower rates than proteins from schistosomula incubated in a serum-containing medium. When schistosomula were incubated at 4 C, a higher degree of reassociation of the same proteins into the parasites was detected. Purified human low density lipoproteins and a fraction containing very low density lipoprotein plus chylomicrons were also able to promote the release of iodinated proteins from the parasites. These observations suggest that serum may play a role in accelerating the turnover of membrane components in schistosomula.