Oral immunization was shown to reduce the passage of a bacterial antigen (BA) through the intestinal wall. The extent of the reduction found was dependent on the technique used for antigen assay, but with 125I-BA in an everted gut sac system, the amount of transported antigen was less than 60 of the amount in a control non-immune system. The inhibitory effect was due to coproantibodies which probably function by complexing and trapping the antigen in the mucous layer. This inhibition of antigen transport seems a prerogative of IgA antibodies since serum-derived antibodies caused concomitant adverse effects.
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