Secretory IgA, IgG, and IgM immunoglobulins isolated simultaneously from colostral whey by selective thiophilic...

In order to evaluate the collective contribution of immunoglobulins to gastrointestinal and immune system development in newborn infants, it would be advantageous to develop a simple and rapid procedure for the selective and quantitative removal of all immunoglobulin classes from colostrum and milk. Toward this end, the major immunoglobulin classes typically present in colostrum (IgM, sIgA, and IgG) have been isolated simultaneously by selective removal from a porcine colostral whey model system using a single-step, preparative scale procedure termed thiophilic adsorption. At neutral pH, the salt-promoted thiophilic affinity of immunoglobulins for the synthetic sulfone-thioether ligands exploits a common (as yet unknown) structural feature of immunoglobulins. The adsorption and recovery procedures operate efficiently under mild buffer conditions permitting the subsequent comparative biochemical analyses of individual immunoglobulin classes for structural and functional heterogeneity. Thus, 1 liter columns of thiophilic adsorbent (T-gel) were employed to obtain pure, structurally intact immunoglobulins from 1 liter batches of porcine colostral whey. The identity and purity of the isolated immunoglobulins were determined under both structure-stabilizing ('native') conditions and denaturing conditions using high-performance size-exclusion chromatography, sucrose density gradient centrifugation, immunodiffusion techniques, SDS-polyacrylamide gradient gel electrophoresis with immunoblotting identification procedures, and two-dimensional electrophoresis. This is the first procedure known to us that allows for the simultaneous one-step isolation (under homologous conditions) of various immunoglobulins with preserved quaternary structure and apparent biological activity.