BackgroundHypertension is a major source of cardiovascular morbidity and mortality. Recent evidence from mouse models, genetic, and cross-sectional human studies suggest increased proportions of selected immune cell subsets may be associated with levels of systolic blood pressure (SBP).MethodsWe assayed immune cells from cryopreserved samples collected at the baseline examination (2000–2002) from 1195 participants from the multi-ethnic study of atherosclerosis (MESA). We used linear mixed models, with adjustment for age, sex, race/ethnicity, smoking, exercise, body mass index, education, diabetes, and cytomegalovirus titers, to estimate the associations between 30 immune cell subsets (4 of which were a priori hypotheses) and repeated measures of SBP (baseline and up to four follow-up measures) over 10 years. The analysis provides estimates of the association with blood pressure level.ResultsThe mean age of the MESA participants at baseline was 64 ± 10 years and 53% were male. A one standard deviation (1-SD) increment in the proportion of γδ T cells was associated with 2.40 mmHg [95% confidence interval (CI) 1.34–3.42] higher average systolic blood pressure; and for natural killer cells, a 1-SD increment was associated with 1.88 mmHg (95% CI 0.82–2.94) higher average level of systolic blood pressure. A 1-SD increment in classical monocytes (CD14++CD16−) was associated with 2.01 mmHG (95% CI 0.79–3.24) lower average systolic blood pressure. There were no associations of CD4+ T helper cell subsets with average systolic blood pressure.ConclusionThese findings suggest that the innate immune system plays a role in levels of SBP whereas there were no associations with adaptive immune cells.