title: Carbohydrate consumption during cycling increases in vitro NK cell responses to IL-2 and IFN-gamma.
abstract: BACKGROUND
  Exercise has been shown to lower blood natural killer cell concentration and activity for up to 24-h after exercise; however, the mechanism underlying this effect is not clearly defined. We have speculated that an exercise-induced change in T-cell control of NK cells is at least partly responsible for the post-exercise suppression. As a follow-up to our previous research, the purpose of this study was to examine the T and NK cells responses during and following moderate/high-intensity endurance exercise.
  
  
  METHODS
  Eight male subjects (20+/-1 y; VO(2peak)=67.22+/-2.79 mL.kg(-1).mL(-1)) were recruited to complete two 1-h (75-80% VO(2peak)) cycling trials in a random counterbalanced order: carbohydrate (CHO) and placebo (PLA). Venous blood samples were collected before (PRE), immediately (POST), 2-h (2H), and 4-h (4H) after exercise. NK (CD3(-)/56(+)) and activated NK (CD3(-)/56(+)/69(+)) number were measured using flow cytometry. NK cell activity (NKCA) was determined using both a (51)Cr release assay (NKCA-51) and activated NK cell number (NKCA-69). Whole blood samples were stimulated with IL-2, IFN-gamma, IL-4, IL-12, and no stimulation for 12-h and then analyzed for NK cell activity using a (51)Cr release assay (NKCA-51).
  
  
  RESULTS
  Leukocyte counts and unstimulated NKCA were not different between CHO and PLA; however, exercise significantly increased NKCA (P<.05). Fold change in IL-2, IFN-gamma, and IL-2+IFN-gamma-stimulated NKCA were significantly greater in CHO compared to PLA (P<.05). No effect of drink was found for IL-4, IL-12, and IL-4+IL-12-stimulated NKCA.
  
  
  CONCLUSIONS
  The fold change in IL-2-stimulated NKCA is consistant with our previous published work. The drink effect for Th1 (but not Th2) cytokines suggests they may play a more significant role in modulating NKCA following a strenuous bout of aerobic exercise when CHO is consumed.
authors.affiliation: University of Houston, Department of Health and Human Performance, Laboratory of Integrated Physiology, Houston, TX 77204-6015, USA. bmcfarlin@uh.edu
authors.forename: Brian K
authors.initials: BK
authors.lastname: McFarlin
authors.forename: Michael G
authors.initials: MG
authors.lastname: Flynn
authors.forename: Ted
authors.initials: T
authors.lastname: Hampton
mesh_terms: D000328:Adult; D001642:Bicycling / Q000502:physiology*; D050260:Carbohydrate Metabolism / Q000276:immunology / Q000502:physiology*; D015444:Exercise / Q000502:physiology; D006801:Humans; D007371:Interferon-gamma / Q000276:immunology*; D007376:Interleukin-2 / Q000276:immunology*; D007694:Killer Cells, Natural / Q000276:immunology* / Q000378:metabolism; D008297:Male; D005082:Physical Exertion / Q000502:physiology; D012016:Reference Values; D018417:Th1 Cells / Q000276:immunology / Q000378:metabolism
chemical_list: D007376:Interleukin-2; D007371:Interferon-gamma