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Blood. 2007 Sep 15;110(6):2190-2. Epub 2007 Jun 6.

Factor H mediated cell surface protection from complement is critical for the survival of PNH erythrocytes.

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  • 1Department of Biochemistry, Center for Biomedical Research, University of Texas Health Science Center, Tyler, TX 75708, USA. viviana.ferrreira@uthct.edu

Abstract

Paroxysmal nocturnal hemoglobinuria (PNH) cells are partially (type II) or completely (type III) deficient in GPI-linked complement regulatory proteins CD59 and CD55. PNH III erythrocytes circulate 6 to 60 days in vivo. Why these cells are not lysed as rapidly by complement as unprotected foreign cells, which normally lyse within minutes, remains undetermined. Factor H plays a key role in the homeostasis of complement in fluid phase and on cell surfaces. We have recently shown that a recombinant protein encompassing the C-terminus of factor H (rH19-20) specifically blocks cell-surface complement regulatory functions of factor H without affecting fluid-phase control of complement. Here we show that PNH II and III cells become highly susceptible to complement-mediated lysis by nonacidified normal human serum in vitro, when the cell surface complement-regulatory functions of factor H are blocked. The results indicate that cells deficient in surface-bound regulators are protected for extended periods of time by factor H.

PMID:
17554058
[PubMed - indexed for MEDLINE]
PMCID:
PMC1976366
Free PMC Article
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