Complement inhibitors (CFI) heavy chain levels decreased in aging ABCA4−/− mice. (A) CFI heavy chain was detected in the retina (Re) and serum (Se) using Western blot under reduced condition. (B) Photometric quantification of CFI heavy chain showed a significant decrease in ABCA4−/− mice at 44 weeks of age compared to wild-type in the retina. Pyruvate dehydrogenase E1 subunit beta (PDHB, 30–35 kDa) was used to normalize the CFI levels in the retina. For the serum, no differences were found between respective genotypes. (C) Immunofluorescence detection of CFI in the cross-sections of mouse eyes. Nuclei were counterstained with DAPI. Stainings were performed on sections from at least three mice per genotype and representative images were chosen. As a negative control, sections were incubated with the secondary antibody (2° ab) only. GCL, ganglion cell layer; IPL, inner plexiform layer; INL, inner nuclear layer; OPL, outer plexiform layer, ONL, outer nuclear layer. Scale bars, 20 µm. (A,B) Bars represent mean values ± SEM from 4 to 10 animals. * p < 0.05, Mann–Whitney U-test.