BTK and neuromyelitis optica: Using a novel assay developed to quantify phagocytosed intracellular myelin basic protein (MBP) in microglia by flow cytometry we found that phagocytosis of myelin was increased after BTK inhibitor treatment, as indicated by the differences in the percentage of MBP+ microglia NMO–IgG versus NMO–IgG + BTKi mice (Additional file 1: Fig. S3A).