Unraveling the C-reactive protein complement-cascade in destruction of red blood cells: potential pathological implications in Plasmodium falciparum malaria.
BACKGROUND
Deficiencies of the complement-regulatory proteins on RBC (RBC(Mal)) of patients with Plasmodium falciparum were reported. Here, we sought to determine the role of affinity-purified C-reactive protein from patients (CRP(Mal)), in modulating the complement-regulatory proteins and downstream effect on complement-cascade.


METHODS
CRP(Mal) was characterized by analytical ultracentrifuge and electrophoretic analysis. Surface plasmon resonance, Western blotting, co-immuno-precipitation, flow-cytometry and ELISA determined the binding of CRP(Mal) with RBC(Mal). Modifications of membranes for RBC(Mal)-CRP(Mal) binding were explored by scanning electron microscopy, osmotic and turbulence fragility, hydrophobicity and oxyhemoglobin release. Flow-cytometry, ELISA, Western blotting and Scatchard analysis monitored the status of complement-regulatory proteins on RBC(Mal). Complement-activation via CRP(Mal) was quantified by C3-deposition and hemolysis.


RESULTS
CRP(Mal) binds specifically to RBC(Mal) through distinct molecules. Such binding altered the normal discoid-shape of RBC(Mal) with increased membrane fluidity and hydrophobicity. In the presence of CRP, RBC(Mal) showed reduced complement-regulatory proteins (CR1 or CD35, CD55 and CD59) with decreased affinity. These changes caused enhanced C3-deposition and complement-mediated hemolysis.


CONCLUSIONS
Taken together, we have established the contributory effect of CRP(Mal) causing decreased complement-regulatory proteins, possibly providing a new mechanism of complement-fueled RBC(Mal) destruction refractory to erythrophagocytosis and may account for pathogenesis of anemia.
Ansar
Waliza
W
Infectious diseases and Immunology Division, Indian Institute of Chemical Biology, Kolkata, India.
Habib
S K Hasan
SK
Roy
Samir
S
Mandal
Chhabinath
C
Mandal
Chitra
C
D000328:Adult; D000818:Animals; D001665:Binding Sites / Q000502:physiology; D015153:Blotting, Western; D002097:C-Reactive Protein / Q000378:metabolism*; D018958:CD55 Antigens / Q000378:metabolism; D018957:CD59 Antigens / Q000378:metabolism; D016022:Case-Control Studies; D004797:Enzyme-Linked Immunosorbent Assay; D004912:Erythrocytes / Q000378:metabolism* / Q000469:parasitology* / Q000648:ultrastructure; D005434:Flow Cytometry; D006801:Humans; D008855:Microscopy, Electron, Scanning; D008875:Middle Aged; D010963:Plasmodium falciparum / Q000472:pathogenicity* / Q000502:physiology; D011485:Protein Binding / Q000502:physiology; D017463:Receptors, Complement 3b / Q000378:metabolism; D020349:Surface Plasmon Resonance; D055815:Young Adult
D018958:CD55 Antigens; D018957:CD59 Antigens; C509991:CR1 protein, human; D017463:Receptors, Complement 3b; D002097:C-Reactive Protein