Reduced Red Blood Cell Surface Level of Factor H as a Mechanism Underlying Paroxysmal Nocturnal Hemoglobinuria
Posted by Adam Awdish on
Pooled Human Serum Off The Clot from Innovative Research was used in the following study:
Lingjun Zhang, Jin Y. Chen, Cassandra Kerr, Brian A. Cobb, Jaroslaw P. Maciejewski & Feng Lin
Leukemia
August 19, 2020
Complement is an important factor in the innate immune response that primarily acts to fight infection and clear apoptotic cells. Once activated, the complement cascade helps in the formation of membrane attack complexes (MAC, C5b-9) on the surfaces of pathogens, causing damage and even lysis of the intruding cells. However, activated complement cannot distinguish healthy host cells from invading pathogens, and thus cells in host tissues must express complement inhibitors on their surfaces to protect against complement attacks.
The absence of the complement inhibitors CD55 and CD59 on the surface of the cell is thought to be the main mechanism underlying the complement-mediated destruction of affected red blood cells (RBCs) in paroxysmal nocturnal hemoglobinuria (PNH) patients.
In this study, researchers identified significantly lower levels of surface-bound Factor H (FH) on affected CD59− RBCs than on normal RBCs. Although this reduction in surface-bound FH on was accompanied by decreased surface sialic acid levels, the enzymatic removal of sialic acids from these RBCs did not seem to affect the levels of surface-bound FH. Finally, the researchers determined that enhanced surface levels of FH on CD55/CD59-deficient RBCs protected against complement-mediated hemolysis. This suggests that a reduced surface level of FH is another important mechanism underlying the pathogenesis of PNH.
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