Intestinal response of sheep to intraperitoneal immunization

The aim of the present study was to develop an immunization procedure which centrally stimulated the IgA system of sheep with the release of antibody-containing cells (ACC) of the IgA class into intestinal lymph. It was found that intraperitoneal injection of ovalbumin resulted in a substantial output of ACC in intestinal lymph. ACC of the IgA class reached a peak 8--9 days after intraperitoneal injection when they comprised 1.4% of cells in lymph. ACC of the IgM and IgG1 classes comprised 3.5 and 2.9% of cells in lymph at this time. The output of ACC of the IgA, IgM and IgG1 classes in lymph at the peak of the response was respectively, 3.7 X 10(6), 9.8 X 10(6) and 8 X 10(6) cells/h. In marked contrast to rats, virtually no ACC appeared in intestinal lymph of sheep following intraduodenal infusion of ovalbumin in animals primed 2 weeks earlier by intraperitoneal injection of antigen in Freund's complete adjuvant (CFA).