title: Caffeine ingestion and antigen-stimulated human lymphocyte activation after prolonged cycling.
abstract: This study investigated the effect of caffeine ingestion on antigen-stimulated T- (CD4(+) and CD8(+) ) and natural killer (NK)- (CD3(-) CD56(+) ) cell activation after prolonged, strenuous cycling. In a randomized cross-over design, nine male endurance cyclists (age: 22 ± 3 years, VO(2peak) : 62 ± 4 mL/kg/min, mean ± SD) cycled for 90 min at 70% VO(2peak) 60 min after ingesting 6 mg/kg body mass of caffeine (CAF) or placebo (PLA). Venous blood samples were obtained before supplementation, pre-exercise, immediately post-exercise and 1 h post-exercise. Whole blood was stimulated with Pediacel (five in one) vaccine. At 1 h post-exercise the number of antigen-stimulated CD4(+) cells expressing CD69 decreased on CAF compared with PLA [15 (17) × 10(6) vs 23 (22) × 10(6) cells/L, P<0.05]. In addition, the geometric mean fluorescence intensity (GMFI) of CD69 expression on antigen-stimulated CD8(+) cells decreased on CAF compared with PLA 1 h post-exercise [78 (10)% vs 102 (24)%, P<0.05]. At the same time-point GMFI of CD69 expression on antigen-stimulated CD3(-) CD56(+) cells was increased on CAF compared with PLA [103 (9)% vs 87 (8)%, P<0.05]. These findings suggest that caffeine reduces antigen-stimulated CD69 expression on T cells while at the same time increases NK-cell activation 1 h after intensive cycling.
authors.affiliation: School of Sport, Exercise and Health Sciences, Loughborough University, Loughborough, UK.
authors.forename: D K
authors.initials: DK
authors.lastname: Fletcher
authors.forename: N C
authors.initials: NC
authors.lastname: Bishop
mesh_terms: D000328:Adult; D015703:Antigens, CD / Q000187:drug effects / Q000378:metabolism; D000945:Antigens, Differentiation, T-Lymphocyte / Q000187:drug effects / Q000378:metabolism; D001642:Bicycling / Q000502:physiology; D002110:Caffeine / Q000276:immunology / Q000494:pharmacology*; D000697:Central Nervous System Stimulants / Q000276:immunology / Q000494:pharmacology*; D018592:Cross-Over Studies; D015444:Exercise / Q000502:physiology; D006801:Humans; D007694:Killer Cells, Natural / Q000187:drug effects* / Q000276:immunology; D037181:Lectins, C-Type / Q000187:drug effects / Q000378:metabolism; D008213:Lymphocyte Activation / Q000187:drug effects*; D008297:Male; D013601:T-Lymphocytes / Q000187:drug effects*; D000099192:CD69 Antigens
chemical_list: D015703:Antigens, CD; D000945:Antigens, Differentiation, T-Lymphocyte; D002110:Caffeine; D000697:Central Nervous System Stimulants; D037181:Lectins, C-Type; D000099192:CD69 Antigens