ERVW-1 and myeloid sarcoma: Regarding innate immunity, syncytin-1 was found to be upregulated in MS patients' brain specific cells involved in neuroinflammation, i.e., astrocytes and microglia, being instead lowly expressed (Antony et al., 2004) or even absent (Mameli et al., 2007a; Perron et al., 2012) in healthy individuals.