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In this study, we aimed to evaluate the association of innate and adaptive immune cell subsets in peripheral blood mononuclear cells (PBMCs) with hip fracture. To conduct this study, we used data from the Cardiovascular Health Study (CHS), a U.S. multicenter observational cohort of community-dwelling men and women aged ≥ 65 years. Twenty-five immune cell phenotypes were measured by flow cytometry from cryopreserved PBMCs of CHS participants collected in 1998–1999. The natural killer (NK), γδ T, T helper 17 (Th17), and differentiated/senescent CD4+CD28− T cell subsets were pre-specified as primary subsets of interest. Hip fracture incidence was assessed prospectively by review of hospitalization records. Multivariable Cox hazard models evaluated associations of immune cell phenotypes with incident hip fracture in sex-stratified and combined analyses. Among 1928 persons, 259 hip fractures occurred over a median 9.7 years of follow-up. In women, NK cells were inversely associated with hip fracture [hazard ratio (HR) 0.77, 95% confidence interval (CI) 0.60–0.99 per one standard deviation higher value] and Th17 cells were positively associated with hip fracture [HR 1.18, 95% CI 1.01–1.39]. In men, γδ T cells were inversely associated with hip fracture [HR 0.60, 95% CI 0.37–0.98]. None of the measured immune cell phenotypes were significantly associated with hip fracture incidence in combined analyses. In this large prospective cohort of older adults, potentially important sex differences in the associations of immune cell phenotypes and hip fracture were identified. However, immune cell phenotypes had no association with hip fracture in analyses combining men and women. [ABSTRACT FROM AUTHOR]

Atherosclerosis is accompanied by a CD4 T cell response to apolipoprotein B (APOB). Major Histocompatibility Complex (MHC)-II tetramers can be used to isolate antigen-specific CD4 T cells by flow sorting. Here, we produce, validate and use an MHC-II tetramer, DRB1*07:01 APOB-p18, to sort APOB-p18-specific cells from peripheral blood mononuclear cell samples from 8 DRB1*07:01+ women with and without subclinical cardiovascular disease (sCVD). Single cell RNA sequencing showed that transcriptomes of tetramer+ cells were between regulatory and memory T cells in healthy women and moved closer to memory T cells in women with sCVD. TCR sequencing of tetramer+ cells showed clonal expansion and V and J segment usage similar to those found in regulatory T cells. These findings suggest that APOB-specific regulatory T cells may switch to a more memory-like phenotype in women with atherosclerosis. Mouse studies showed that such switched cells promote atherosclerosis., Competing Interests: DISCLOSURES There are no conflicts of interest.