Chromatographic separation and purification of secretory IgA from human milk

Defatted and decaseinated human milk was concentrated and was fractionated on a preparative DEAE cellulose column. Elution with various concentrations of sodium chloride in Tris-HCl buffer (pH 8.0, 0.01 M) resulted in fractions that were rich in either secretory immunoglobulin A (SIgA) (0.1 M NaCl) or free secretory component (SC) (0.05 M NaCl). The fractions, which were eluted with 0.10 M NaCl from the preparative column, were further fractionated on a G-200 Sephadex column. Repeated fractionation on this column resulted in a single purified fraction, which contained very high SIgA activity and showed immunological cross-reaction with both SC and serum IgA. Additional studies indicated that this fraction was homogeneous as shown by immunoprecipitin and disc gel electrophoresis. Injection of this purified SIgA into rabbits resulted in the production of monospecific antisera.