CONDITIONING OF CYCLOPHOSPHAMIDE-INDUCED LEUKOPENIA IN HUMANS

This study evaluated whether decrements in peripheral leukocyte counts induced by cyclophosphamide can be conditioned in humans. Ten subject s being treated for multiple sclerosis received four intravenous treat ments with cyclophosphamide (unconditioned stimulus) paired with a con ditioned stimulus. Subjects received conditioned stimulus plus 10 mg o f cyclophosphamide during one of the next two treatments in a double-b lind manner. Eight of 10 subjects (P = 0.044) displayed decreased peri pheral leukocyte counts following conditioned stimulus. This change ma y have resulted from classical conditioning processes.