Circulating immune cell landscape and T‐cell abnormalities in patients with moyamoya disease

Abstract Background Moyamoya disease (MMD) stands as a prominent cause of stroke among children and adolescents in East Asian populations. Although a growing body of evidence suggests that dysregulated inflammation and autoimmune responses might contribute to the development of MMD, a comprehensive and detailed understanding of the alterations in circulating immune cells associated with MMD remains elusive. Methods In this study, we employed a combination of single‐cell RNA sequencing (scRNA‐seq), mass cytometry and RNA‐sequencing techniques to compare immune cell profiles in peripheral blood samples obtained from patients with MMD and age‐matched healthy controls. Results Our investigation unveiled immune dysfunction in MMD patients, primarily characterized by perturbations in T‐cell (TC) subpopulations, including a reduction in effector TCs and an increase in regulatory TCs (Tregs). Additionally, we observed diminished natural killer cells and dendritic cells alongside heightened B cells and monocytes in MMD patients. Notably, within the MMD group, there was an augmented proportion of fragile Tregs, whereas the stable Treg fraction decreased. MMD was also linked to heightened immune activation, as evidenced by elevated expression levels of HLA‐DR and p‐STAT3. Conclusions Our findings offer a comprehensive view of the circulating immune cell landscape in MMD patients. Immune dysregulation in patients with MMD was characterized by alterations in T‐cell populations, including a decrease in effector T‐cells and an increase in regulatory T‐cells (Tregs), suggest a potential role for disrupted circulating immunity in the aetiology of MMD.