Extended Data Figure 9.

Secretion of C4, and specificity of the monoclonal anti-C4 antibody for C4 protein in human brain tissue and cultured primary cortical neurons.

(a) Brain tissue (from an individual affected with schizophrenia) was stained with a fluorescent secondary antibody, C4 antibody, or C4 antibody that was pre-adsorbed with purified C4 protein. Confocal images demonstrate the loss of immunoreactivity in the secondary-only and pre-adsorbed conditions.

(b) Primary human neurons were stained with a fluorescent secondary antibody, C4 antibody, or C4 antibody that was pre-adsorbed with purified C4 protein. Confocal images demonstrate the loss of immunoreactivity in the secondary-only and pre-adsorbed conditions. Scale bar for all images = 25 µm.

(c) Secretion of C4 protein by cultured primary neurons. Western blot for C4 protein analysis. (+) Purified human C4 protein. (−) Unconditioned medium, a negative control. (HN-conditioned) shows the same medium after conditioning by cultured human neurons at days 7 (d7) and 30 (d30). Details of Western blot protocol, antibody catalog numbers and concentrations used are in Methods. C4 molecular weight ~210 kDa.