Cholera antitoxin titrations: A comparative study of fat-cell, ileal-loop, and rabbit-skin assays

The levels of serum antibodies to cholera toxin can be measured by any of three test systems. Each of these assays (isolated fat cell, rabbit skin, and ileal loop) give similar values although there are differences in sensitivity among the systems. The variety of antisera and toxins tested makes it very likely that a single antigen- antibody reaction is being measured by each assay method. Recent proof of the hypothesis that cholera toxin acts by raising levels of cyclic adenosine-3',5'-mono- phosphate in tissues exposed to toxin may explain how the apparent diversity of biological end points observed in the respective test systems may be achieved through a common mechanism of action. It is likely that direct enzymatic methods can be developed to speed and simplify further the assay of this toxin.