Decay-accelerating factor (CD55) deficiency

DAF, or CD55, is a control protein of the classical and alternative pathways. It is deficient in red blood cells from patients with paroxysmal nocturnal hemoglobinuria (PNH). DAF is a glycosyl phosphatidylinositol (GPI)-anchored membrane protein found on erythrocytes, lymphocytes, granulocytes, endothelium, and epithelium. The main function of DAF is to protect cells from complement-mediated cytolysis and it also plays a role in T cell activation. PNH is a rare condition, which causes increased sensitivity of red cells to lysis by complement due to absence of MIRL and DAF.

Alternative names

CD55 deficiency

DAF deficiency


  • Defects of complement regulatory proteins


Autosomal recessive


*125240 Decay-accelerating factor for complement; DAF

Cross references

Phenotypically related immunodeficiencies

CD59 deficiency


Incidence is not known.