Femoral atherosclerotic plaques are less inflammatory than carotid plaques histologically, but limited cell-level data exist regarding comparative immune landscapes and polarization at these sites. We investigated intraplaque leukocyte phenotypes and transcriptional polarization in 49 patients undergoing femoral ( n = 23) or carotid ( n = 26) endarterectomy using single-cell RNA-Seq (scRNA-Seq; n = 13), flow cytometry ( n = 24), and IHC ( n = 12). Comparative scRNA-Seq of CD45 ⁺ -selected leukocytes from femoral ( n = 9; 35,265 cells) and carotid ( n = 4; 30,655 cells) plaque revealed distinct transcriptional profiles. Inflammatory foam cell–like macrophages and monocytes comprised higher proportions of myeloid cells in carotid plaques, whereas noninflammatory foam cell–like macrophages and LYVE1-overexpressing macrophages comprised higher proportions of myeloid cells in femoral plaque ( P < 0.001 for all). A significant comparative excess of CCR2 ⁺ macrophages in carotid versus plaque was observed by flow cytometry in a separate validation cohort. B cells were more prevalent and exhibited a comparatively antiinflammatory profile in femoral plaque, whereas cytotoxic CD8 ⁺ T cells were more prevalent in carotid plaque. In conclusion, human femoral plaques exhibit distinct macrophage phenotypic and transcriptional profiles as well as diminished CD8 ⁺ T cell populations compared with human carotid plaques

Acute neutrophil responses following myocardial infarction (MI) play a central role in remodeling, contributing to both repair and potential maladaptive responses. Although prior studies have investigated circulating immune cell indices at a single time point during hospitalization for MI, limited data exist on acute intra-individual changes in circulating immune profiles during evolving MI. We analyzed clinical measurements, such as the count and proportion of immune cell components in a serial complete blood count, with differential tests conducted for patients hospitalized with ST-elevation MI (STEMI) in various hospitals in the Northwestern Medicine system from 1 January 2002 to 1 August 2024. Patients with STEMI diagnosis, troponin peaks ≥ 5 ng/mL, and cell count and proportion data prior to the troponin peak and within 24 h after the troponin peak were included. Primary analyses investigated the associations between the troponin peak and peri-STEMI changes in immune cell subsets. Multivariable-adjusted Cox models were used to investigate associations between these peri-STEMI immune cell changes and mortality at 1 year and 3 years. Among the 694 STEMI patients meeting the inclusion criteria, a higher troponin peak was associated with a modest peri-MI increase in neutrophil proportion. Higher adjusted peri-STEMI increases in neutrophil count and proportion were strongly associated with mortality at one and three years [hazard ratio (HR) = 1.31 (95% confidence interval (CI) 1.15–1.49) and HR = 1.27 (95% CI 1.14–1.45) per 1000 cells/μL absolute neutrophil increase, respectively]. Individuals with higher STEMI-related neutrophil increases had higher mortality at one year and three years, independent of the extent of troponin elevation.