Enhancement by Cadmium of Double-Diffusion Precipitin Reactions

Abstract

Low concentrations of cadmium ions have been discovered specifically to enhance antigen-antibody precipitation. This effect has been studied by incorporating cadmium salts in agar used in a slight modification of Ouchterlony's double-diffusion precipitin technique. Preliminary experiments are reported which characterize the activity of cadmium nitrate upon rabbit and guinea pig antisera against tuberculoprotein antigen. Although usually cnhancing, at certain very low concentrations cadmium nitrate irreversibly inhibited some antigen-antibody precipitation reactions. At its optimum enhancing concentras tion, this salt apparently accelerates as well a-increases specific precipitation. Antiserum rather than antigen is affected in the system used. Not all antisera are sensitive to cadmium, for several of those from rabbits which were tested were unaffected by cadmium's presence in the reacting agar. However, all guinea pig antisera utilized were sensitive. The effect does not seem to be simply one of partial antibody denaturation.