SIRPA and myeloid sarcoma: Han et al. further demonstrated that CD47 is expressed in normal myelin and in foamy macrophages and reactive astrocytes within active MS lesions (not in reactive astrocytes within chronic MS lesions) and displays Janus-like opposing effects on MS pathogenesis by interacting with SIRP-α, which is likely caused by the expression of CD47 in different cell types and locations [45].