C3 and membranous glomerulonephritis: The study found that eight proteins of the complement pathway (C1q, C3, C4, C5, C6, C7, C8, and C9) and 5 complement regulators (complement receptor type 1[CR1], factor H [FH], FH-related protein 2 [FHR2], vitronectin, and clusterin) were elevated in kidney biopsy samples of primary membranous nephropathy compared to healthy controls.