Lymphocyte distribution in mouse submandibular lymph nodes in response to acute treadmill exercise

The submandibular lymph nodes (LN), part of the nasal-associated lymphoid tissue (NALT), are involved in local immune responses in the eye, upper respiratory tract (URT), and oral mucosa. Although athletes have been reported to be at increased risk for URT and ocular infections, little is known about the impact of exercise on LN included in the NALT. The purpose of this study was to examine the impact of intense acute exercise on submandibular lymphocyte distribution. Female C57BL/6 mice were randomly assigned to a nonexercised control condition or a single session of treadmill exercise (32 m·min^-1, 8° grade for 90 min) and sacrificed immediately, 2, and 24 h after exercise. Running resulted in a significant increase in plasma corticosterone immediately following exercise compared with other times (p < 0.001). Percentages and total numbers of CD3⁺ and CD4 ⁺CD8^- T lymphocytes in submandibular LN were significantly lower 24 h after exercise compared with controls. The percentage of pan-NK and CD19⁺ B cells increased immediately and 24 h after exercise, respectively, but the total numbers were not affected. The results suggest that decreased percentages and absolute numbers of T cells in submandibular LN following a single session of intense exercise may be partially mediated by increased corticosterone concentrations and may have consequences for ocular health among athletes.