Deep Immune Profiling of Patients with STAT1 Gain-of-Function: Revealing New Mechanisms of Pathology

Background: Patients with heterozygous signal transducer and activator of transcription 1 (STAT1) gain-of-function (GOF) pathogenic variants exhibit an array of clinical phenotypes including susceptibility to multiple infections, autoimmunity, and cancer predisposition. Previous studies to characterize the pathways involved and explore therapeutic interventions have been constrained by the technology to perform in-depth immunophenotyping. Mass cytometry has allowed us to perform extensive immune profiling of patients with inborn errors of immunity (IEI) to help gain a better understanding of disease pathology. STAT1 gain-of-function (GOF) mutations have demonstrated higher levels of phosphorylated STAT1 in response to type I and II interferons, but the response to other cytokines is less understood. Using advanced cytometry, we demonstrate a unique pattern of STAT1 phosphorylation in response to IL-6 stimulation in T-cell subsets and this differential pattern may play a role in T-cell differentiation and memory in STAT1 GOF patients.