C5AR1 and myeloid sarcoma: Subsequent immunohistochemical studies analyzing the presence and localization of key complement components (C3, factor B, C1q), activation products (C3b, iC3b, C4d, TCC/MAC), regulators (factor H, C1-inhibitor, clusterin) and receptors (C3aR, C5aR1) in established MS lesions found that, although variable between individuals, the presence of complement proteins and activation products in and around white matter lesions is a consistent feature of progressive MS (Ingram et al., 2014; Loveless et al., 2018), echoing the conclusions from Breij et al. (2008).