In Xenopus transgenic models, approximately 75% of immune cells expressing BTK were microglia, and the remainder astrocytes, suggesting a high bioavailability of BTK in the CNS of this model system.15 Microglia initiate demyelination and immune filtration in MS pathogenesis during the early phases of the condition, while in later stages they can promote both neurodegeneration and remyelination.34 Microglia BTK could be an important therapeutic target, if the pro-inflammatory function could be curtailed in early phases of the condition and the pro-remyelinating function promoted. The gene discussed is BTK; the disease is myeloid sarcoma.