SHORT-TERM ATTENUATION OF NATURAL-KILLER-CELL CYTOTOXIC ACTIVITY IN WHEELCHAIR MARATHONERS WITH PARAPLEGIA

Objective: To investigate homeostasis of the immune system in athletes with spinal cord injuries during and after racing a wheelchair marath on. Design: The study examined changes in the number and function of n atural killer (NK) cells in nine male wheelchair marathon athletes (sp inal cord injuries between T5 and T12) who completed the 15th Oita Int ernational Wheelchair Marathon Race. Blood samples were obtained the d ay before, immediately after, and 1 day after the race. Blood samples were also obtained from seven age-matched control subjects with spinal cord injuries but who did not exercise regularly. Results: The number of peripheral leukocytes increased (p < .01) immediately after the ra ce. In contrast, the number of peripheral NK cells and NK cell cytotox ic activity significantly decreased from 310 +/- 130/mu L to 133 +/- 6 1/mu L and from 42.6% +/- 3.0% to 38.2% +/- 3.2%, respectively (mean /- SD), immediately after the race. Plasma cortisol levels were increa sed after the race. However, all parameters returned to control levels within 24 hours. Measurements in control subjects did not change thro ughout the experiment. Conclusion: These findings suggest that racing a marathon suppressed peripheral NK cell number as well as NK cell cyt otoxic activity in wheelchair athletes and that this was probably medi ated by increased postrace cortisol levels. Wheel chair marathon athle tes are advised to take extra precaution to avoid infection within 24 hours after racing because of the transient suppression of NK cell cyt otoxic activity during this period. (C) 1998 by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medici ne and Rehabilitation.