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      Deposition of Mannan Binding Protein and Mannan Binding Protein-Mediated Complement Activation in the Glomeruli of Patients with IgA Nephropathy

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          Mannan binding protein (MBP) is a C-type lectin and has a high affinity to mannose and N-acetyl glucosamine. It is also known to activate C4 and C2 without C1 component, which is called ‘lectin pathway’. We now report the presence of MBP and MBP-mediated complement activation in renal glomeruli of IgA nephropathy patients using an immunohistochemical method. In 7 of 42 cases with IgA nephropathy, MBP was detected in the glomerular mesangial area and colocalized with IgA1. In 19 cases with other types of IC-mediated glomerulonephritis including lupus nephritis and membranous nephropathy or without nephritis, MBP was not detected in the glomerulus. The C2- and/or C4-positive rate was 87.5% in the MBP-positive group and 20% in the MBP-negative group of IgA nephropathy. In addition, MBP-positive cases showed marked mesangial cell proliferation, lower creatinine clearance (53.4 ± 10.0 vs. 77.8 ± 4.7 ml/min) and higher urinary protein excretion (2.5 ± 0.9 vs. 0.9 ± 0.2 g/day) compared with MBP-negative cases. These findings suggested that MBP was involved in glomerular complement activation through the lectin pathway and thus induced glomerular injury of IgA nephropathy. Since oligosaccharide chain alterations such as reduced sialic acid and galactose of IgA1 molecule have been reported in IgA nephropathy patients, MBP might bind to the IgA1 molecule via interaction between MBP and sugar chain.

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          Most cited references 6

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          Engineering galactose-binding activity into a C-type mannose-binding protein.

           K Drickamer (1992)
          Calcium-dependent or C-type carbohydrate-recognition domains are homologous protein modules found in a variety of animal lectins. Selective binding of sugars by these domains is essential for glycoprotein clearance, cell-cell adhesion and pathogen neutralization. Although various C-type carbohydrate-recognition domains share sequence identity ranging from 20 to 55%, their sugar-binding characteristics vary widely. The structure of a mannose-binding carbohydrate-recognition domain in complex with a saccharide ligand suggests that two glutamic acid-asparagine pairs are essential determinants of ligand binding by this domain. In C-type lectins that bind galactose with higher affinity than mannose, one of these pairs is replaced by glutamine-aspartic acid. Here we shift the sequence of the mannose-binding protein to correspond to that found in galactose-binding domains in order to test the importance of these residues in sugar-binding selectivity. This simple switch in the position of a single amide group alters the binding activity of the domain so that galactose becomes the preferred ligand.
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            Glycosylation changes of IgG associated with rheumatooid arthritis can activate complement via the mannose-binding protein

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              Collectins: collagenous C-type lectins of the innate immune defense system.

              Collectins are humoral lectins found in mammals and birds. They are oligomers whose subunits comprise three polypeptide chains each containing a collagenous section and a C-terminal lectin domain. They are related structurally and functionally to the first component of the classical complement pathway, C1q, and seem to serve important roles in innate immunity through opsonization and complement activation. The lectin domains bind carbohydrates on microorganisms, while the collagenous regions are ligands for the collectin receptor on phagocytes and also mediate C1q-independent activation of the classical complement pathway.

                Author and article information

                S. Karger AG
                December 1998
                07 December 1998
                : 80
                : 4
                : 408-413
                a Department of Medicine III, Okayama University Medical School, Okayama, and b Department of Biological Chemistry, Faculty of Pharmaceutical Sciences, Kyoto University, Kyoto, Japan
                45212 Nephron 1998;80:408–413
                © 1998 S. Karger AG, Basel

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                Page count
                Figures: 3, Tables: 1, References: 23, Pages: 6
                Self URI (application/pdf): https://www.karger.com/Article/Pdf/45212
                Original Paper

                Cardiovascular Medicine, Nephrology

                Mannan binding protein, IgA nephropathy, Lectin pathway


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