ADA2 and myeloid sarcoma: Whereas decreased ADA2 activity as a growth factor for M2-polarized macrophages can redirect them, and the microglial cells, to the M1 pro-inflammatory phenotype that, at early stages of MS, leads to severe tissue damage in the CNS (Chu et al., 2018; Watanabe et al., 2019; Kutryb-Zajac et al., 2021).