Significant differences have been reported for plasma levels of components (C1s, MASP-2, C3, C4 and C9), regulators (FH and C1inh) and activation products (iC3b, Bb, C4a, C4b and TCC) between MS patients and controls and between MS patients in remission, relapse or with progressive disease [150,160–164]. This evidence concerns the gene C4B and myeloid sarcoma.