C2 and myeloid sarcoma: The levels of complement proteins, including C1q, C2, C4, and C5 in MS CSF and serum are altered in comparison to healthy individuals and between different MS clinical subtypes (Sellebjerg et al., 1998; Jongen et al., 2000; Finehout et al., 2005; Stoop et al., 2008; Ingram et al., 2010; Aeinehband et al., 2015; Magliozzi et al., 2019a; Zelek et al., 2019).