Effects of strenuous exercise on Th1/Th2 gene expression from human peripheral blood mononuclear cells of marathon participants

• Gene expression profile of cytokines and their related genes from PBMC of marathon participants was analyzed using Human Th1-Th2-Th3 RT2 Profiler PCR Array.
• The majority of genes up-regulated post-marathon was Th2 associated.
• The ratios of IFN-γ/IL-4 mRNA and T-bet/GATA3 mRNA were significantly decreased one week post-marathon.
• Th1/Th2 balance was shifted toward a predominant Th2 response post-marathon.

Physical stressors, such as strenuous exercise, can have numerous effects on the human body including the immune system. The aim of this study was to evaluate the gene expression profile of Th1/Th2 cytokines and related transcription factor genes in order to investigate possible immune imbalances before and after a marathon. Blood samples were collected from 16 normal volunteers 24–48 h before and one week after completing a marathon race. Gene expression of Th1 and Th2 related cytokines from human peripheral blood mononuclear cells (PBMC) was analyzed using Human Th1-Th2-Th3 RT2 Profiler PCR Array and qRT-PCR that measured the transcript levels of 84 genes related to T cell activation. We found that PBMC express a characteristic Th2-like gene profile one week post-marathon compared to pre-marathon. The majority of genes up-regulated one week post-marathon such as IL-4, GATA3, and CCR4 were Th2 associated. For Th1-related genes, CXCR3 and IRF1 were up-regulated one week post-marathon. There was a trend of down-regulation of two Th1 related genes, T-bet and STAT1. Th3-related gene expression patterns did not change in the study. The ratios of both IFN-γ/IL-4 and T-bet/GATA3 gene expressions were significantly lower one week after marathon. These findings suggest that a Th1/Th2 immune imbalance persisted at least 1 week after completion of a marathon which offers a mechanistic rationale for the increased risk of upper respiratory tract infections often reported after strenuous exercise.