title: A comparison of the binding of secretory component to immunoglobulin A (IgA) in human colostral S-IgA1 and S-IgA2.
abstract: A detailed investigation of the binding of secretory component to immunoglobulin A (IgA) in human secretory IgA2 (S-IgA2) was made possible by the development of a new method of purifying S-IgA1, S-IgA2 and free secretory component from human colostrum using thiophilic gel chromatography and chromatography on Jacalin-agarose. Sodium dodecyl sulphate-polyacrylamide gel electrophoresis of unreduced pure S-IgA2 revealed that, unlike in S-IgA1, a significant proportion of the secretory component was bound non-covalently in S-IgA2. When S-IgA1 was incubated with a protease purified from Proteus mirabilis the secretory component, but not the alpha-chain, was cleaved. This is in contrast to serum IgA1, in which the alpha-chain was cleaved under the same conditions - direct evidence that secretory component does protect the alpha-chain from proteolytic cleavage in S-IgA. Comparisons between the products of cleavage with P. mirabilis protease of free secretory component and bound secretory component in S-IgA1 and S-IgA2 also indicated that, contrary to the general assumption, the binding of secretory component to IgA is different in S-IgA2 from that in S-IgA1.
authors.affiliation: Department of Pathology, Immunology Unit, College of Medicine and King Khalid University Hospital, Riyadh, Saudi Arabia.
authors.forename: Adel
authors.initials: A
authors.lastname: Almogren
authors.forename: Bernard W
authors.initials: BW
authors.lastname: Senior
authors.forename: Michael A
authors.initials: MA
authors.lastname: Kerr
mesh_terms: D015153:Blotting, Western; D002850:Chromatography, Gel / Q000379:methods; D003126:Colostrum / Q000276:immunology*; D004591:Electrophoresis, Polyacrylamide Gel / Q000379:methods; D006801:Humans; D018928:Immunity, Mucosal; D007071:Immunoglobulin A, Secretory / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D008970:Molecular Weight; D010447:Peptide Hydrolases; D037121:Plant Lectins; D011513:Proteus mirabilis / Q000201:enzymology; D012635:Secretory Component / Q000378:metabolism*
chemical_list: D007071:Immunoglobulin A, Secretory; D037121:Plant Lectins; D012635:Secretory Component; C043696:jacalin; D010447:Peptide Hydrolases