Immunoglobulin A Preparation from Human Pooled Plasma Using Plasma Fractionation and Ion Exchange Chromatography

In this study we have prepared the IgA solution from normal human plasma using plasma fractionation and ion exchange chromatography. Using fractionation of plasma with cold ethanol (starting with 8% ethanol), fraction III was prepared as a suitable source for IgA preparation. Then it was treated with caprylic acid for separation of impurities. For enrichment of IgA, ion exchange chromatography using Sephadex DEAE A-50 on a Pharmacia glass column was carried out. By fractionation of pooled human plasma and then treatment with caprylic acid, the amount of immunoglobulins showed an increase from 17% to 80% measured by immunoturbidimetric method. Then the ion exchange column chromatography by Sephadex DEAE A-50 was carried out. In washing solution 65 % of loaded IgG and only 17% of loaded IgA were found. In elution solution 32% of loaded IgG and 79% of loaded IgA were obtained, which showed the ion exchange chromatography is a promising method for preparation of enriched IgA solution. Because of the similarity between IgA and IgG, techniques based on net charge and molecular differences would not give a high yield in IgA isolation. As IgA has a negative charge at the pH 8.1, Sephadex DEAE A-50 which is able to bind proteins at relatively high ionic strength was chosen for ion exchange chromatography. After column ion exchange chromatography, the concentration of obtained IgA was three times more enriched in comparison with the concentration of IgA in normal plasma.