Lymphopenia and impaired immunological activities of splenocytes during the immune response to cholera enterotoxin.

Immunization of mice with small doses of purified cholera enterotoxin (CE) stimulated the rapid appearance of antitoxin antibody-forming cells in the spleen. Peak anti-CE PFC responses occurred between 5 and 7 days. Shortly following CE inoculation, however, the weight and cellular content of the spleen were markedly altered. A two-fold reduction occurred in the spleen weight and the nucleated cell content 48 h after injection of 1.0 μg CE. Surface immunoglobulin (sIg)- and Thy 1.2 (θ)-bearing splenocytes were reduced four- to six-fold at this time. Functional studies demonstrated that the capping response of sIg-bearing spleen cells, the ability of B lymphocytes to synthesize or release antibody to sheep erythrocytes (SRBC) and the helper function of thymocytes in the anti-SRBC response were impaired in CE-treated mice. Impairment of immunological activities was dose dependent but transitory, since both the cellular content, the capping response, and the immune competence of spleen cells returned to normal values between 7 and 10 days. The rapid alterations in splenic cellularity and functional activity of T and B cells are compatible with the marked nonspecific immunosuppression caused by CE when given to mice prior to SRBC and other antigens such as bacterial lipopolysaccharides.