CONDITIONED MANIPULATION OF NATURAL-KILLER (NK) CELLS IN HUMANS USINGA DISCRIMINATIVE LEARNING PROTOCOL

There is growing evidence indicating that the immune function can be m odified by classical conditioning techniques. This phenomenon, initial ly explored in animals, is further documented by studies providing evi dence that the human immune response can also be influenced by classic al conditioning processes. In the present study, we tested the hypothe sis that human immune parameters can be modulated by discriminative le arning processes. Using a classical discriminative conditioning design , healthy volunteers were provided with a CS + (sherbet sweet/white no ise), which was repeatedly paired with an injection of epinephrine (un conditioned stimulus, US). After epinephrine injections(0.2 mg subcuta neously), a transient increase of natural killer (NK) cell activity (u nconditioned response, UR) could be observed. A second stimulus comple x (herbal sweet/auditory stimulus, conditioned stimulus, CS-) remained without reinforcement. After repeated presentation of the stimuli, re -exposure of the CS+ on the test trial 1 resulted in a significantly i ncreased number of NK positive (NK+) cells and in slightly elevated NK cell activity. No alteration of NK cells, however, could be observed after presentation of the CS-. A second re-exposure of the CS+ on test trial 3, again resulted in a marked increase of NK+ cell number as we ll as in significantly elevated NK cell activity. The data presented h ere extend previous observations of conditioned alteration of immune r esponses in humans and indicate that the human organism might be able to react differentially to external stimuli, which have been associate d with different immunological consequences.