Building on mouse data, Colli et al. demonstrated that PD-L1 is expressed on β cells of pancreatic islets of patients with T1DM and is upregulated by the interferon (IFN)-α and IFN-γ via induction of the Janus kinase (JAK)/signal transducer and activator of transcription (STAT)/ Interferon Regulatory Factor 1 (IRF1) pathway—a signaling cascade that integrates the IFN signaling. The gene discussed is IFNA1; the disease is type 1 diabetes mellitus.