A comparison of three isolation methods for obtaining immunoglobulin A from turkey bile

Turkey IgA was isolated from bile by three methods: ammonium sulfate precipitation, polyethylene glycol (PEG) extraction, and lambda-carrageenan extraction. The isolated immunoglobulin fractions were compared using double diffusion, immunoelectrophoresis (IE), and enzyme-linked immunosorbent assay (ELISA). Results indicated that all three methods of isolation are sufficient for the initial isolation step for purification of the immunoglobulin fraction in turkey bile. Because of contaminating IgG, IgM, and other high-molecular-weight proteins, further purification by column chromatography is needed to isolate pure IgA. The lambda-carrageenan extraction method appears to be the method of choice for precipitating the immunoglobulin fraction in bile, because of the high antibody activity after extraction. Like ammonium sulfate precipitation, lambda-carrageenan and PEG extraction are not sufficient as single-step purification methods and should be used as the initial step in the purification of IgA.