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Please use this identifier to cite or link to this item: http://hdl.handle.net/123456789/5664

Title: Irreversible aggregation of the Fc fragment derived from polymeric but not monomeric serum IgA1—Implications in IgA-mediated disease
Authors: Almogren, Adel
Kerr, Michael A.
Keywords: IgA structure
IgA nephropathy
IgA protease
Fc region
Issue Date: 2008
Publisher: Elsevier
Citation: Molecular Immunology: 45; 87–94
Abstract: IgA is by far the most abundant immunoglobulin in humans. It is found in serum and in secretions (SIgA). Unlike any other class of immunoglobulin, each form of IgA occurs naturally in different polymerisation states. In serum, the predominant form of IgA is IgA1 of which around 90% is monomeric and 10% is dimeric or polymeric. The proportion of dimeric/polymeric IgA increases in a number of important diseases, such as IgA nephropathy and in chronic liver disease. In both, there is evidence that further aggregation of dimeric/polymeric IgA is the cause of the characteristic tissue deposition. To investigate the effect of role of IgA polymerisation on the structure and function of IgA, we purified different molecular forms of IgA1 from myeloma serum (monomer, dimer and trimer) and SIgA1 from colostrum. Structural features of these different IgA1 forms were examined following proteolysis using Neisseria gonorrhoeae IgA1 type 2 protease and Streptococcus pneumoniae IgA1 protease. These IgA1 proteases cleave IgA1 at the hinge region and produce Fc and Fab fragments. Western blot analysis demonstrated that the Fc fragments of serum dimeric and trimeric but not monomeric IgA1 aggregated to form multimers resistant to disruption in SDS-PAGE under non-reducing conditions. Size exclusion chromatography under native conditions of cleaved serum dimeric IgA1 demonstrated that aggregation occurs because of structural changes in the IgA per se and was not an effect of the SDS-PAGE system. In the same assay, SIgA1 (dimeric) did not aggregate after digestion. The results suggest an important, previously unrecognised, property of dimeric/polymeric serum IgA1, which might explain its propensity to aggregate and deposit in tissues
URI: http://hdl.handle.net/123456789/5664
ISSN: 0161-5890
Appears in Collections:King Khalid Hospital

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