The effects of age and viral serology on γδ T-cell numbers and exercise responsiveness in humans

•γδ T-cell numbers and proportions decline with increasing chronological age.•Latent CMV infection is associated with increased γδ T-cell numbers in the young.•Exercise evokes an increase in circulating γδ T-cell numbers.•Older subjects have an impaired ability to redeploy γδ T-cells with exercise. γδ T-cells are cytotoxic effector cells that preferentially migrate to peripheral tissues and recognize many types of antigen. We examined the effects of age and viral serology on the exercise responsiveness of γδ T-cells. Blood was collected from 17 younger (age: 23–35yrs) and 17 older (50–64yrs) healthy males matched for cytomegalovirus (CMV), Epstein-Barr virus, herpes simplex virus-1 and Parvovirus B19 serologic status before and after a single bout of cycling exercise. Older had lower numbers and proportions of γδ T-cells than younger, while CMV was associated with increased numbers and proportions of γδ T-cells in younger but not older. Exercise evoked a ∼2-fold increase in circulating γδ T-cell numbers. The magnitude of this response was 3-times greater in younger compared to older, and 1.6-times greater in younger CMV-infected compared to younger non CMV-infected. To conclude, γδ T-cell numbers and exercise responsiveness decreases with age and may contribute to impaired immunosurveillance after acute acute physical stress.