Pre-Existing Hypertension Dominates γδT Cell Reduction in Human Ischemic Stroke

T lymphocytes may play an important role in the evolution of ischemic stroke. Depletion of gamma delta T cells has been found to abrogate ischemia reperfusion injury in murine stroke. However, the role of gamma delta T cells in human ischemic stroke is unknown. We aimed to determine gamma delta T cell counts and gamma delta T cell interleukin 17A (IL-17A) production in the clinical setting of ischemic stroke. We also aimed to determine the associations of gamma delta T cell counts with ischemic lesion volume, measures of clinical severity and with major stroke risk factors. Peripheral blood samples from 43 acute ischemic stroke patients and 26 control subjects matched on race and gender were used for flow cytometry and complete blood count analyses. Subsequently, cytokine levels and gene expression were measured in gamma delta T cells. The number of circulating gamma delta T cells was decreased by almost 50% (p = 0.005) in the stroke patients. gamma delta T cell counts did not correlate with lesion volume on magnetic resonance diffusion-weighted imaging or with clinical severity in the stroke patients, but gamma delta T cells showed elevated levels of IL-17A (p = 0.048). Decreased gamma delta T cell counts were also associated with older age (p = 0.004), pre-existing hypertension (p = 0.0005) and prevalent coronary artery disease (p = 0.03), with pre-existing hypertension being the most significant predictor of gamma delta T cell counts in a multivariable analysis. gamma delta T cells in human ischemic stroke are reduced in number and show elevated levels of IL-17A. A major reduction in gamma delta T lymphocytes also occurs in hypertension and may contribute to the development of hypertension-mediated stroke and vascular disease.