CD55 and paroxysmal nocturnal hemoglobinuria: Several routes toward clinical application for MP have been explored since then, including the use of recombinant GPI-anchored CD4 as a strategy for human immunodeficiency virus (HIV)-mediated gene therapy (44) and the use of the natural, non-recombinantly GPI-AP CD55 and CD59, to treat paroxysmal nocturnal hemoglobinuria (PNH) (45, 46).