Role of decay-accelerating factor in regulating complement activation on the erythrocyte surface as revealed by gene targeting

Abstract

Decay-accelerating factor (DAF) is a glycosylphosphatidylinositol (GPI)-anchored membrane protein that inhibits both the classical and the alternative pathways of complement activation. DAF has been studied extensively in humans under two clinical settings: when absent from the erythrocytes of paroxysmal nocturnal hemoglobinuria (PNH) patients, who suffer from complement-mediated hemolytic anemia, and in transgenic pigs expressing human DAF, which have been developed to help overcome complement-mediated hyperacute rejection in xenotransplantation. Nevertheless, the exact role of DAF in regulating complement activation in vivo on the cell surface and the species specificity of this molecule remain to be fully characterized. To address these issues, we have used gene targeting to produce mice lacking GPI-anchored DAF. We found that erythrocytes from mice deficient in GPI-anchored DAF showed no increase in spontaneous complement activation in vivo but exhibited impaired regulation of zymosan-initiated bystander and antibodytriggered classical pathway complement activation in vitro, resulting in enhanced complement deposition. Despite a high level of C3 fixation, no homologous hemolysis occurred. It is noteworthy that GPI-linked DAF knockout erythrocytes, when tested with human and guinea pig sera, were more susceptible to heterologous complement lysis than were normal erythrocytes. These results suggest that DAF is capable of regulating homologous as well as heterologous complement activation via the alternative or the classical pathway. They also indicate that DAF deficiency alone is not sufficient to cause homologous hemolysis. In contrast, when the assembly of the membrane-attack complex is not properly regulated, as in the case of heterologous complement activation or in PNH patients, impaired erythrocyte DAF activity and enhanced C3 deposition could lead to increased hemolytic reaction.

Decay-Accelerating Factor Confers Protection Against Complement-Mediated Podocyte Injury in Acute Nephrotoxic Nephritis

“…Thus, it has been hypothesized that Crry plays the dominant role in control of the C3 step of complement activation in the mouse, overwhelming the importance of DAF (Quigg et al, 1998a;Quigg and Holers, 1995). The fact that Daf1 knock-out mice are viable, fertile, and show no major abnormalities constitutively (Lin et al, 2001;Sun et al, 1999) has contributed to this view.…”

Maturation and enucleation of primitive erythroblasts during mouse embryogenesis is accompanied by changes in cell-surface antigen expression

“…We found that EryPs expressed several surface antigens found on EryDs, including Ter119, 39 CD71, 39 CD24, 41 CD55, 42 and CD147. 44 Simultaneous analysis of Ter119 and CD71 by flow cytometry revealed a developmental progression for circulating EryPs reminiscent of that found for EryDs.…”

“…To characterize further the development of circulating EryP, we stained for 3 additional surface antigens that have been detected on definitive erythroid cells. The glycoproteins CD24, 55 CD55, 42 and CD147/Basigin 44 were strongly expressed on all circulating EryP/ GFP ϩ cells at the developmental stages examined (Table 3; Figure 4). The GFP Ϫ cells (presumed EryD) also expressed CD24, CD55, and CD147, as expected, at levels comparable to those measured for EryP/GFP ϩ cells.…”

“…We examined the expression of surface antigens on EryP/GFP ϩ cells to identify differentiation 42,43 and CD147, 44 which have been detected on definitive erythroid cells, were also expressed strongly on circulating EryP/GFP ϩ cells from E9.5 onward (Table 3; data not shown). Surprisingly, expression of several adhesion molecules was up-regulated on a subset of circulating EryP/GFP ϩ cells.…”

Critical Protection from Renal Ischemia Reperfusion Injury by CD55 and CD59

“…CD55 knockout (CD55 Ϫ/Ϫ ) mice and CD59 knockout (CD59 Ϫ/Ϫ ) mice were generated as described previously (18,19). These mice were deficient in the widely distributed GPI-decay-accelerating factor gene and CD59a gene (20 -22), respectively.…”