Depression and Immunity: Central Corticotropin- Releasing Factor Activates the Autonomic Nervous System and Reduces Natural Killer Cell Activity
Michael R. Irwin, M.D. University of California, San Diego
A number of clinical studies have described relationships between severe life stress, depression, and alterations in cellular immunity. However, few studies have evaluated the physiological mechanisms by which the central nervous system might coordinate immune function. In this chapter, recent data from clinical and preclinical investigations in our laboratory are presented that focus on two primary objectives: (a) to characterize further the relationship between psychological processes and immune function, and (b) to examine the mechanisms by which the central nervous system communicates with immune cells. Using an animal model, central corticotropin-releasing factor has been found to modulate natural killer (NK) cell activity by activation of the sympathetic nervous system.
Evaluation of depression-related changes in natural killer cell activity has been of primary interest in our laboratory for several reasons. First, NK cells are a distinct subpopulation of lymphocytes that are thought to be important in the resistance to viral infections before the immunologic response of other cells can be mounted. Substantial evidence in animals supports the hypothesis that NK cells are involved in the control of experimental herpes simplex virus (HSV) and cytomegalovirus (CMV) infections ( Lotzova & Herberman, 1986). For example, an enhanced susceptibility to HSV-1 has been found in mice who are selectively depleted of NK activity and receive HSV-1 simultaneously, but not in mice in which