(a) C1q binds immobilized malondialdehyde-modified LDL
(MDA-LDL) and oxLDL but not native LDL or gelatin. (b) ApoE
isoforms in NHS were added to MDA-LDL-coated microtiter plates and C4b
deposition was determined by specific antisera.
(c,d) IgM, MDA-LDL, and Aβ fibrils but not
soluble Aβ activate complement and cause C3b deposition. BSA, gelatin as
negative controls; (e, f) ApoE3 was incubated with
either (e) C2 or (f) C4 in the presence of C1s. C2
and C4 were cleaved to their active forms C2a (α′30) and C4b
(α′83) via C1s as revealed by the cleavage products in Western
blot analyses; (g) ApoE3 has no cofactor activity for factor I
in the cleavage of C4b to inactive iC4b. ApoE3 was incubated together with
factor I, C4BP and C4b, and cleavage products were detected by Western blot
analysis as indicated (α′25 and α′13). Full scanned
blot images in e,f,g are available from source data figures. Data in a-d
represent means ± SEM of three independent experiments. Two-tailed
Student's t-test. Data in e,f,g are representative from 3 independent
experiments.