Department of Hematology, Nephrology and Rheumatology, Akita University Graduate School of Medicine, Akita, Japan.
Nephrol Dial Transplant. 2012 May;27(5):1937-41. doi: 10.1093/ndt/gfr571. Epub 2011 Oct 3.
It is known that a predominant glomerular deposition of IgG4 is characteristic of idiopathic membranous nephropathy (MN) and that significant deposition of other IgG subclasses is also observed in lupus MN. However, there is no report focusing on the distribution of glomerular IgG subclass deposits in MN patients with anti-U1 ribonucleoprotein (RNP) antibody.
We evaluated clinicopathological features and the distribution patterns of glomerular IgG subclass deposits in seven MN patients with positive anti-RNP antibody and negative antibodies to double-stranded DNA (dsDNA) and Smith antigen (Sm) (RNP-MN group) and in seven age- and sex-matched lupus MN patients with positive anti-dsDNA antibody and negative antibodies to RNP and Sm (L-MN group).
Mixed connective tissue disease was diagnosed in four patients in the RNP-MN group. Two patients in the RNP-MN group and three patients in the L-MN group developed nephrotic syndrome. Renal insufficiency was not present in all patients in both groups. Hypocomplementemia was found in two patients in the RNP-MN group and six patients in the L-MN group. In the RNP-MN group, positive stainings for glomerular IgG1, IgG2, IgG3 and IgG4 were observed in one, seven, zero and five patients, respectively. On the contrary, in the L-MN group, positive stainings for glomerular IgG1, IgG2, IgG3 and IgG4 were observed in seven, seven, seven, and six patients, respectively.
This is the first study showing striking differences in the distribution of glomerular IgG subclass deposits between RNP-MN and L-MN groups. RNP-MN and L-MN may result from different immunological mechanisms.
已知特发性膜性肾病（MN）的特征是 IgG4 为主的肾小球沉积，狼疮性 MN 中也观察到其他 IgG 亚类的显著沉积。然而，目前尚无专门针对抗 U1 核糖核蛋白（RNP）抗体阳性 MN 患者肾小球 IgG 亚类沉积分布的报道。
我们评估了 7 例抗 RNP 抗体阳性、抗双链 DNA（dsDNA）和 Smith 抗原（Sm）抗体阴性的 MN 患者（RNP-MN 组）和 7 例抗 dsDNA 抗体阳性、抗 RNP 和 Sm 抗体阴性的狼疮性 MN 患者（L-MN 组）的临床病理特征和肾小球 IgG 亚类沉积分布模式。
在 RNP-MN 组中，4 例患者被诊断为混合性结缔组织病。在 RNP-MN 组中有 2 例患者和在 L-MN 组中有 3 例患者出现肾病综合征。两组患者均无肾功能不全。在 RNP-MN 组中，有 2 例患者存在低补体血症，在 L-MN 组中，有 6 例患者存在低补体血症。在 RNP-MN 组中，分别有 1、7、0 和 5 例患者的肾小球 IgG1、IgG2、IgG3 和 IgG4 呈阳性染色。相反，在 L-MN 组中，分别有 7、7、7 和 6 例患者的肾小球 IgG1、IgG2、IgG3 和 IgG4 呈阳性染色。
这是第一项研究表明 RNP-MN 和 L-MN 组之间肾小球 IgG 亚类沉积分布存在显著差异。RNP-MN 和 L-MN 可能由不同的免疫机制引起。
