Western blot was performed using Anti-C4BPA Polyclonal Antibody (Product # PA5-76234) and bands corresponding to 93 kDa and 52 kDa of C4BPA was observed in the reported positive models- Hep G2 and Mouse Epididymis relative to DU 145, BeWO and Mouse Lung which are low expressing models along with an uncharacterized band (*) at ~40 kDa in the cell lines tested. Whole cell extracts (30 µg lysate) of Hep G2 (Lane 1), DU 145 (Lane 2), BeWO (Lane 3), tissue extracts (30 µg lysate) of Mouse Lungs (Lane 4) and Mouse Epididymis (Lane 5) were electrophoresed using NuPAGE™ 10% Bis-Tris Protein Gel (Product # NP0302BOX). Resolved proteins were then transferred onto a nitrocellulose membrane (Product # IB23001). The blot was probed with the antibody (1:1,200 dilution) and detected by ECL with Goat anti-Rabbit IgG (Heavy Chain), Superclonal™ secondary, HRP (Product # A27036, 1:4,000 dilution). ECL was performed using Novex® ECL Substrate Reagent Kit (Product # WP20005). C4 protein, composed of alpha, beta and gamma chain, forms a heterotrimer of ~93 kDa alpha chains via disulphide linkage as detected by this antibody (10.4049/jimmunol.165.5.2518) and a ~52 kDa protein corresponding to mouse and rat specific isoforms of C4BPA. It is also reported to be secreted by the epithelial cells surrounding the epididymis for sperm maturation in a region-specific, androgen dependent and species specific manner in addition to being synthesized in the liver.