Effect of anti-properdin IgG on formation of C3
convertase
The effect of total IgG, positive for anti-properdin autoantibodies on
the interaction of properdin with C3b, C3bB and C3bBb was analyzed in
real time using a ProteOn XPR36 SPR equipment (BioRad,
Marne-la-coquette, France). Properdin was covalently immobilized to a
GCL sensor chip (BioRad), following the manufacturer’s procedure.
Protein G purified IgG from LN patients, positive for anti-properdin
autoantibodies (but negative for anti-C3b and anti-FB), and healthy
donors were injected for 300s at dilution 1:15 in 10 mM Hepes, 50 mM
NaCl, 10 mM MgCl, 0.005% Tween 20, pH 7.4 buffer. The same buffer was
separately injected to serve as a control. Following 300s of
dissociation, C3b (13µg/ml), C3b (13µg/ml) + Factor B (10µg/ml) and C3b
(13µg/ml) + Factor B (10µg/ml) + Factor D (0,5µg/ml) (Complement
Technology) were injected for 300s of association, followed by 300s of
dissociation.