CD55 and multiple sclerosis: CD55 is considered to be a positive regulator when it comes to tumorigenesis and malaria infection, whereas a negative regulator of the CHAPLE (CD55 deficiency with hyper-activation of complement, angiopathic thrombosis, and severe protein-losing enteropathy) syndrome, paroxysmal nocturnal hemoglobinuria, multiple sclerosis, and autoimmune diseases [20].