© 1990 by CRC Press, Inc. A large resource of older literature exists which documents many aspects of conditioned “immunobiologic” responses. 1 These conditioning experiments involved both the specific and nonspecific immune responses. Specific antibody responses were measured by agglutinin titers, and the nonspecific responses ranged from peritoneal exudates to complement levels and activity of lysozyme. These studies demonstrated many instances of enhanced responses due to conditioning. 1 The difficulty replicating these early studies has been attributed to the use of different species, varied environmental conditions, the schedule of conditioned stimulus (CS) and unconditioned stimulus (US) pairing, and the interval after the CS for measuring the conditioned response (CR). 1.