We performed robot-assisted, live cell– and flow cytometry–based immunofluorescence assays against two CNS (MOG, AQP4) and two peripheral nervous system (AChR, MuSK) surface Ags in four large and clinically well-characterized cohorts of patients with autoimmune disease (RA, T1D, SLE, and neurologic [MS, NMOSD, OND]) and matched HDs. The gene discussed is MUSK; the disease is systemic lupus erythematosus.