Regulation of the in vitro early anamnestic antibody response by exogenous cholera enterotoxin and cyclic AMP.

Keyhole limpet hemocyanin was injected into the hind foot pads of rabbits. Six days later cell suspensions were prepared from the popliteal lymph nodes. Various amounts of hemocyanin (1 ng to 100 mug) were added to 1 times 10-7 cells to induce an anamnestic antibody response. Various amounts of cholera enterotoxin, which stimulates the enzyme adenylate cyclase, or dibutyryl cyclic adenosine 3'5'-monophosphate (AMP), were added to the cultures with or without hemocyanin. De novo synthesis of antibody, protein, deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) from radioactive precursors was assayed. The addition of cholera toxin or dibutyryl cyclic AMP for the first 24 hr with optimal (1 mug) or supraoptimal (100 mug) amounts of hemocyanin enhanced antibody synthesis by at least 100 to 200%. Addition of the toxin or dibutyryl cyclic AMP for the same period to cells minus hemocyanin or with suboptimal amounts (1 to 100 ng) of antigen failed to enhance antibody synthesis. Addition of these agents for 72 to 120 hr to hemocyanin-induced cultures consistently inhibited antibody synthesis. These agents slightly inhibited DNA and RNA synthesis. The increase in protein synthesis caused by the toxin or dibutyryl cyclic AMP was almost totally accounted for by the increase in antibody synthesis. Neither toxin nor cyclic nucleotide promoted the antibody response in the presence of antibody to rabbit thymus-derived lymphocytes; these lymphocytes as well as bursa-equivalent lymphocytes were required for potentiation of the response. Macrophages were not required either for induction of the anamnestic response or for enhancement of this synthesis by cyclic nucleotide or cholera toxin. Both IgM and IgG antibody synthesis were regulated by exogenous cholera toxin and dibutyryl cyclic AMP. A number of possible cellular mechanisms of regulation of the antibody response through the cyclic AMP pathway were discussed. These included the effects of modifications of this pathway on the activities of T lymphocytes early (0 to 24 hr) and B lymphocytes late (72 to 120 hr) in the response and on the apparent reversal of high zone tolerance.