Normotensive African American Males Exhibit Augmented CD4 to CD8 T Cell Ratios Compared to Caucasian American Males
Authors: Martin Zachary T. , Akins John D. , Despain Kevin R. , Fadel Paul J. , Brothers R. Matthew , Trott Daniel W. 
Published: June 2021

Hypertension is more prevalent in African Americans (AA) (45%) than the general U.S. population (33%). Notably, young AA males without overt signs of hypertension exhibit impaired brachial artery vasodilation, cerebrovascular reactivity, and microvascular function, but the cause of these vascular impairments remains incompletely understood. Although T cells are critical in rodent models of hypertension, less is known regarding the role of T cells in human hypertension, particularly as it relates to the greater prevalence of hypertension and vascular dysfunction in AA. Recent work in humans demonstrates that lower circulating CD4 to CD8 T cell ratios and elevated populations of CD28−CD57+ T cells are associated with advanced age, vascular dysfunction, and hypertension. Whether there is an alteration in the T cell phenotype that precedes hypertension in AA is unknown. Thus, we assessed T cell CD4, CD8, CD28, and CD57 cell surface markers in AA and Caucasian Americans (CA) and tested the hypothesis that AA would have elevated CD28−CD57+ cell fractions and reduced CD4 to CD8 ratios compared to CA.METHODSTwelve ml of blood from 11 young, apparently healthy males (6 AA, age 21 ± 1 years, BMI: 24.8 ± 1.8 kg/m2; 5 CA, age 25 ± 4 years, BMI: 23.1 ± 2.3 kg/m2) were obtained for analysis during a fasted venous blood draw. Peripheral blood mononuclear cells were isolated by density centrifugation. Cells were then stained with antibodies against CD3 (pan T cells), CD4 (T helper cells), and CD8 (cytotoxic T cells). Cells were also stained for antibodies against CD28 and CD57, which are cell surface markers associated with T cell aging. Cells were then analyzed via flow cytometry.RESULTSThe percentage of total T cells was similar in AA and CA (60.1 ± 4.3% vs. 60.7 ± 2.6%; p = 0.89). The percentage of total T cells that were CD4 cells in AA was higher relative to CA (61.5 ± 3.7% vs. 49.7 ± 1.4%; p = 0.03). Alternatively, the percentage of total T cells that were CD8 cells in AA was lower relative to CA (26.3 ± 2.8% vs. 39.6 ± 0.9%; p < 0.01). The CD4 to CD8 ratio was higher in AA than CA (2.53 ± 0.39 vs. 1.26 ± 0.04; p = 0.02). Among CD4 cells, the fraction of CD28−CD57+ cells in AA was similar to that found in CA (0.63 ± 0.24% vs. 0.52 ± 0.31%; p = 0.78). Similarly, among CD8 cells, the fraction of CD28−CD57+ cells in AA was comparable to that found in CA (9.8 ± 4.6% vs. 13.5 ± 4.0%; p = 0.56).CONCLUSIONRacial differences in CD28−CD57+ cell fractions among both CD4 and CD8 T cells were not detected. However, contrary to our hypothesis, the CD4 to CD8 ratio was elevated in AA compared to CA. This was driven by higher CD4 and lower CD8 percentages in AA. Collectively, these results suggest that previously observed impairments in vascular function in young healthy AA males may not be attributable to a reduced CD4 to CD8 ratio nor an accumulation of CD28−CD57+ cells.Support or Funding InformationUTA Start‐up funds to R. Matthew BrothersThis abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.