Inhibition of mouse natural killer activity by cholera toxin

The treatment of mouse spleen cells with cholera toxin (CT) extracted from Vibrio cholerae greatly reduced natural killer (NK) activity. The inhibition of NK activity was rapidly induced by CT treatment and persisted in the absence of CT. Even a very small amount of CT, such as 0.1 ng/ml, was effective in inhibiting NK activity. The inhibitory effect of CT on NK activity was lost upon preabsorption of CT with brain tissues, but not upon preabsorption with liver or kidney tissues.