Background: Inflammation plays an important role in ischemic stroke (IS) pathophysiology. Gamma/delta+ TCR (gdTCR), CD8+gdTCR, and CD4+ gdTCR lymphocytes are newly recognized contributors to innate immune systems responses. In experimental stroke models gdTCR lymphocytes have been found to contribute substantially to cerebral infarct growth and have the potential to contribute to immune memory after stroke. We aimed to determine whether changes in gdTCR cellular count and lymphocyte activity occur after human stroke, and if differences exist between first-ever and recurrent IS. Methods: First-ever IS patients (n=20), recurrent IS patients (n=29) and matched healthy control subjects (n=28) were studied. Blood was drawn within 72 hours of stroke onset and was stained with CD3 (PE-TR), gdTCR (PE), CD4 (FITC) and CD8 (PE-Cy5) monoclonal antibodies. The percentages of circulating gdTCR lymphocytes were evaluated by fluorescent-activated cell counter and analyzed using “FlowJo” software. The expression of selected inflammatory and stroke-related genes, based on previous reports, was measured in gdTCR lymphocytes isolated from 7 first-ever IS patients and 14 recurrent IS patients. Magnetic bead separation was used for cellular isolation and messenger ribonucleic acid expression was measured using digital polymerase chain reactions. Statistical analyses used Mann-Whitney U tests and chi-square tests. Results: The numbers of CD8+gdTCR cells were higher in all IS patients vs. control subjects (p=.04) and in recurrent IS patients vs. control subjects (p=.01). No difference was seen between first ever IS patients and control subjects (p=.4). Comparison of gdTCR cellular gene expression between recurrent IS patients and first-ever IS patients showed significantly higher expression of MMP9 (p=.02) and SLC2A3 (p=.04) in recurrent IS patients. TLR2 and IL23R were also borderline significantly higher in recurrent IS patients (0.05<p<0.1). No differences in gdTCR or CD4+ gdTCR counts were found between IS patients and controls. Conclusion: Alterations in gdTCR gene expression and in levels of the CD8+TCR subset in patients with recurrent stroke may indicate a potential role of the innate system in immune memory after ischemic stroke.

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