Known and Plausible Modulators of Depressed Immune Functions Following Spinal Cord Injuries

Abstract

Recent evidence suggests that depression of immune function occurs early after spinal cord injury (SCI) and is maintained thereafter. Deviations from immune function observed in healthy persons with intact neuraxes include natural killer cell number and cytotoxicity, T cell function and activation, macrophage phagocytosis, levels of interleukins (IL)-2 and -6, the soluble IL-2R receptor, and intracellular adhesion molecules. While a single etiology explaining these abnormalities has not been identified, decentralization of the autonomic nervous system is the most likely cause. Otherwise, many persons with SCI, who sustain episodic autonomic overstimulation, are among the most physically deconditioned of all humans, and often select a diet rich in fat and low in protein. All of these are associated with suppressed immune function in persons without SCI. Those with SCI may also be (over)exposed to drugs and medications that suppress immune function, including methylprednisolone administered immediately after traumatic injury. No evidence suggests that the immune profiles of persons with SCI favor disease and illness resistance. As opportunistic infections of the urinary tract, lungs, and skin represent major causes of morbidity for those aging with SCI, attention to, or intervention on, immune suppressive states, traits, behaviors, diets, and medications may represent a means through which host defenses of persons with SCI can be fortified and their illness proclivities reduced.