An islet-resident macrophage antioxidant program preserves β cell physiology.

Pancreatic islet-resident macrophages (IRMs) display an activated phenotype and contribute to islet development and remodeling, yet their origin, heterogeneity, and functional roles remain poorly understood. Using complementary fate-mapping systems, we show that, in adult mice, around half of IRMs originate from circulating monocytes and undergo minimal turnover. Integrated multiple single-cell RNA sequencing analyses of mouse and human islets identified four major IRM cell states that collectively reveal their inflammatory and metabolic activation. Among these, a transcriptional program driven by the cystine-glutamate antiporter SLC7A11 and enriched in CD9high IRMs was associated with enhanced antioxidant defense, mitochondrial activity, and iron-lipid metabolic pathways. We found that Slc7a11-expressing IRMs preserve β cell redox homeostasis and insulin secretion, both at baseline and under stress. These findings position IRMs as specialized immune sentinels in the endocrine pancreas and identify SLC7A11 as a key macrophage-intrinsic safeguard against oxidative stress, with broad implications for islet resilience and metabolic health.