Regulation of natural immunity (NK activity) by conditioning

A paradigm is described for the conditioning of the NK response. Mice were exposed to a classical conditioning procedure in which saccharin and lithium chloride (LiCl) served as the conditioned stimulus (CS) paired with an injection of either poly I:C or cytoxan, the unconditioned stimulus (US). Poly I:C was used as the US for enhancement and cytoxan served as the US for suppression. Subsequent exposure to the CS either enhanced or suppressed the NK activity in the conditioned animals. Our studies showed that only one association was needed for the learning to take place, training to consumption of water was not necessary, and the conditioned (enhanced) response could be recalled as soon as 7 days after pairing of the US and CS.