Selective removal, recovery, and characterization of immunoglobulins from human colostrum.

Investigations into the mechanisms by which Ig in human colostrum influence the development and maturation of both the gastrointestinal and the immune systems of human milk-fed term and preterm infants have been restricted by the paucity of purified human milk Ig. We have developed a simple adsorption procedure for the selective removal and quantitative recovery (95-100%) of intact Ig (secretory IgA, IgG, and IgM) present in human colostral whey. The procedure exploits the rapid, ionic-strength dependent, thiophilic adsorption of Ig during a single pass of colostral whey through a column of beaded agarose with immobilized thioether-sulfone ligands (Anal Biochem 1986;159:217-226). The purity and composition of the adsorbed Ig were verified by SDS-PAGE and sensitive silver-staining protein detection procedures; proteins of approximately 78-80 kD (secretory component), 50-60 kD (heavy chain), and 25 kD (light chain) were observed. The identity, structural integrity, and relative concentrations of the recovered Ig were confirmed by high-performance size-exclusion chromatography, Ouchterlony immunodiffusion, rocket immunoelectrophoresis and ELISA. These results were analyzed and compared with reported values for the concentration of human milk Ig. Thus, the use of thiophilic adsorption appears to facilitate 1) selective removal of Ig from colostrum, enabling the evaluation of remaining components for growth- and immune-potentiating properties, and 2) selective immobilization and recovery of Ig from colostrum under conditions consistent with preserved biologic activity.