Intestinal resistance to cholera toxin in mouse. Antitoxic antibodies and desensitization of adenylate cyclase.

Mice were immunized perorally with cholera toxin (CT), cholera B-subunit (CB), or buffer as control. The response of anti-CT antibodies of the IgG, IgA and IgM class in bile, IgA being predominating, were similar in both immunized groups. The same number of anti-CT containing plasma cells (ACC) were determined in the intestinal lamina propria of CT - as well as of CB-immunized mice 20 days after the last immunization, while ACC at day 4 in the CB group were 50% higher than in the CT group. In contrast to the vigorous antibody response to CT in both groups of immunized mice, only animals immunized with CT displayed resistance to CT-induced intestinal hypersecretion and to CT stimulation of adenylate cyclase. The CB-treated group responded to CT with fluid accumulation and enzyme activation similar to controls. The results suggest that intestinal resistance to CT in mouse is due to desensitization of adenylate cyclase rather than to CT-neutralizing antibodies.