Nonpathogenicity of antiintestinal antibody in the rabbit

Rabbits were immunized with intestinal extract prepared from rabbits, guinea pigs, and germ-free rats. The resultant serum antibody response to intestinal antigen was determined by gel precipitation and direct tissue immunofluorescence. Forty-eight hours prior to sacrifice of each immunized animal, a portion of the duodenum, ileum, and colon were traumatized to bring circulating antibody into contact with the tissue. Sections for histology and direct immunofluorescence were taken from the area of trauma, just adjacent to the area, and 10 cm from it. The humoral immune response, the presence of tissue bound immunoglobulin, and tissue histology were compared. The area of trauma in normal and immunized animals showed the same histologic changes. In each animal, tissue just adjacent to the area of trauma and 10 cm from it were histologically identical. The pathologic alterations in the immunized animals were similar to those associated with malabsorption in man. Direct immunofluorescence of the intestinal tissue revealed bound immunoglobulin in histologically normal and abnormal tissue. Precipitating antibody to intestine was present in the serum of rabbits with normal and abnormal histology. Thus, antiintestinal antibody as dected by precipitation in gel and direct tissue immunofluorescence does not appear to be a factor in the pathogenesis of this model of immunologically induced histologic changes in the intestine.