ARG1 and myeloid sarcoma: Increased ARG1 expression in PBMCs from MS patients is supported by a study of macrophages from the blood of disease‐modifying treatment (DMT)‐free patients with established MS.20 These cells expressed increased ARG1 in vitro, and they were more susceptible to activation with an enhanced ability, relative to macrophages from normal people, to skew towards inducible NOS‐ or ARG‐expressing cells in the presence of LPS or IL‐4, respectively.20