Lhotta K, Würzner R, König P
Department of Internal Medicine, Innsbruck University Hospital, Austria.
Nephrol Dial Transplant. 1999 Apr;14(4):881-6. doi: 10.1093/ndt/14.4.881.
Mannose-binding lectin (MBL), a member of the collectin family, binds to various oligosaccharides and activates the classical pathway of complement independent from C1q. At present it is unknown whether this so-called lectin pathway of complement activation plays a role in the pathogenesis of human glomerulonephritis.
Direct immunofluorescence of 84 renal biopsies using an MBL-specific monoclonal antibody and antibodies directed against IgG, IgA, IgM, C1q, C3, and terminal complement complex (TCC) was performed. Serum MBL levels of 50 patients were determined by enzyme-linked immunosorbent assay.
MBL was detected in the glomeruli of patients with lupus nephropathy (15 of 16), membranous nephropathy (10/15), membranoproliferative glomerulonephritis type I (5/6) and anti-GBM nephritis (2/4). MBL deposition paralleled that of immunoglobulins, C1q, C3, and TCC but was less intense as compared to C1q. Focal segmental deposits of MBL were present in focal segmental glomerulosclerosis (4/6), IgA nephropathy (3/11), amyloidosis AL (1/4), and advanced renal fibrosis (2/2). Here MBL staining was identical to IgM and C3 and considered an unspecific entrapment of MBL in sclerotic lesions in these cases. No significant difference in MBL serum levels was observed between normal controls and patients with lupus nephritis, membranous nephropathy, membranoproliferative glomerulonephritis, focal segmental sclerosis, minimal change disease or IgA nephropathy. In patients suffering from membranous nephropathy with (n=10) or without (n=5) glomerular MBL deposits serum creatinine, C3, C4, serum protein, and proteinuria were not statistically different.
MBL is present in the glomeruli of patients with glomerulonephritis involving deposition of IgG and activation of the classical pathway of complement. We propose that MBL binds to agalactosyl oligosaccharides of IgG that terminate in N-acetylglucosamine. The extent to which the lectin pathway of complement contributes to overall complement activation in the glomeruli remains unknown, but is likely to be marginal.
甘露糖结合凝集素（MBL）是胶原凝集素家族的一员，可与多种寡糖结合，并独立于C1q激活补体经典途径。目前尚不清楚这种所谓的补体凝集素途径是否在人类肾小球肾炎的发病机制中起作用。
使用MBL特异性单克隆抗体以及针对IgG、IgA、IgM、C1q、C3和末端补体复合物（TCC）的抗体，对84份肾活检组织进行直接免疫荧光检测。采用酶联免疫吸附测定法测定50例患者的血清MBL水平。
在狼疮性肾炎患者（16例中的15例）、膜性肾病患者（15例中的10例）、I型膜增生性肾小球肾炎患者（6例中的5例）和抗肾小球基底膜肾炎患者（4例中的2例）的肾小球中检测到MBL。MBL沉积与免疫球蛋白、C1q、C3和TCC的沉积平行，但与C1q相比强度较弱。在局灶节段性肾小球硬化症（6例中的4例）、IgA肾病（11例中的3例）、AL型淀粉样变性（4例中的1例）和晚期肾纤维化患者（2例中的2例）中存在MBL的局灶节段性沉积。在这些病例中，MBL染色与IgM和C3相同，被认为是MBL在硬化病变中的非特异性截留。在正常对照组与狼疮性肾炎、膜性肾病、膜增生性肾小球肾炎、局灶节段性硬化症、微小病变病或IgA肾病患者之间，未观察到MBL血清水平的显著差异。在有（n = 10）或无（n = 5）肾小球MBL沉积的膜性肾病患者中，血清肌酐、C3、C4、血清蛋白和蛋白尿在统计学上无差异。
MBL存在于伴有IgG沉积和补体经典途径激活的肾小球肾炎患者的肾小球中。我们提出MBL与以N - 乙酰葡糖胺结尾的IgG的半乳糖基寡糖结合。补体凝集素途径在肾小球中对整体补体激活的贡献程度尚不清楚，但可能很小。
