A method for preparation of IgA from bovine mammary secretions

A method for preparing purified IgA from bovine mammary secretions is described. Whey was initially fractionated by gel filtration and fractions containing IgA were pooled, concentrated and digested with pepsin. The digest was rechromatographed on the same type of gel twice and the resulting IgA preparation tested for purity by an enzyme immunoassay procedure. Five different preparations tested were found to contain no measureable IgM or IgG2 and 0.8% to 1.1% IgG1 on a weight basis. If colostral whey was digested with pepsin prior to chromatography, the IgA preparations contained 1.1% to 2% IgG1 and no measureable IgM and IgG2. The procedure provides a reasonably easy method of eliminating most of the contaminating IgG1 (dimeric) and allows preparation of quantities of IgA for immunochemical studies and standardization of serological techniques.