Adoptive transfer of immune enhancement of experimental ulcerative colitis

Previous experiments with the carrageenan model for ulcerative colitis have shown that the inflammatory response in guinea pigs can be enhanced by immunization with and subsequent feeding of Bacteroides vulgatus to experimental animals. The present studies showed that only certain strains of B. vulgatus are capable of provoking immune enhancement of ulcerative colitis. Animals were fed carrageenan and various strains of viable B. vulgatus after immunization with a strain of B. vulgatus isolated from a guinea pig with experimentally induced colitis. Histological comparison of immune and nonimmune groups revealed that immune animals which received B. vulgatus from a patient with inflammatory bowel disease had a significantly (P less than 0.025) greater number of histopathological lesions at 21 days than did nonimmune animals. Immune animals receiving B. vulgatus isolated from a clinically normal source did not show any significant difference in disease status when compared to nonimmune animals. Additional experiments showed that adoptive transfer of spleen cells from animals immunized with B. vulgatus to nonimmune recipient animals is effective in transferring the immune enhancement demonstrated in actively immunized animals. Animals which received immune spleen cells with concurrent feeding of B. vulgatus showed a significant (P less than 0.005) increase in inflammation over control groups, in the absence of high titers of circulating antibody. These experiments indicate that B. vulgatus strain-specific factors are important to immune enhancement of experimental disease and also suggest an involvement of the cell-mediated immune system in this model.