Cd28 Expression On Cd4+ T Cells Is Not Affected By Strenuous Exercise In Untrained Individuals

Abstract

Optimal T cell activation requires a two-signal process. The first signal is engagement of the TCR-CD3 complex and the second, or costimulatory, signal is the classical binding of a T cell CD28 receptor with an APC-bound CD80 or CD86. A marker of senescent T cells is a lack of CD28 expression and it has been posited that CD28 expression may decrease following strenuous exercise. PURPOSE: To quantify exercise induced changes in CD28 expression on CD4+ cells obtained from human subjects. METHODS: Utilizing a cross over design, untrained subjects completed a control and exercise visit. The control visit consisted of 30 min of seated rest while the exercise session entailed 3 sets x 10 reps squat at 70% 1-RM, 3x10 leg press at 70% 1-RM, and 3x10 leg extensions at 70% 1-RM with 2 min rest between sets. Venous blood samples were obtained pre and post each visit. CD4+ T cell isolation from peripheral blood was conducted through negative selection using a Human CD4+ T cell enrichment kit. CD4+ T cells were plated at 1.5 x 106 cells/ml in 200 μl of ImmunoCult T-cell expansion media directly after isolation and costimulated through CD3+CD28 or no stimulation. Cells were incubated for 1 and 3 d at 37°C in a humidified incubator with 5% CO2 and then analyzed by flow cytometry. Data were analyzed using two-way RMANOVAs. RESULTS: There were no significant differences in CD28 expression between the exercise and control conditions in either the stimulated (p = .27) or non-stimulated (p = .62) samples. These data suggest that suppression of CD4+ cell activation following strenuous exercise is likely not a result of dysfunction in CD28, a major costimulatory receptor. CONCLUSIONS: Changes in T cell activation following strenuous exercise are likely derived from a plurality of sources, but without direct assessment of discrete elements of the activation cascade we will be unable to understand how exercise changes immune function. Future work should focus on elements upstream of T cell clonal expansion in order to identify mechanisms for exercise induced changes in immunocompetence. Supported by an award through the Dr. George F. Haddix President’s Faculty Research Fund at Creighton University.