Role of G-CSF and C-CSF receptor gene polymorphisms for the development of lupus nephritis

系统性红斑狼疮(SLE)是一种复杂的多基因疾病，是一种典型的抗体介导的自身免疫性疾病，其特征是产生针对多种自身抗原的自身抗体和免疫复合体(IC)型组织炎症，最突出的是肾脏。在SLE易感(NZB X NZW)F1小鼠中，由于NZB和NZW菌株的易感基因的作用，IC型狼疮性肾炎比亲本NZB更严重。我们对(NZB X NZW)F1与NZB或NZW小鼠回交的狼疮性肾炎易感基因进行全基因组扫描，发现位于第4染色体Clq和G-CSF受体基因附近的NZB基因和位于第11染色体G-CSF基因附近的NZW基因与重症肾炎有关。对Clq和G-CSF受体基因的序列分析和功能分析表明，第4号染色体上的候选基因可能是Clq。G-CSF基因序列分析表明，NZB和NZW的3‘非编码区存在序列多态性。NZW组巨噬细胞G-CSF基因表达水平和巨噬细胞产生G-CSF能力显著高于NZB组，可能是由于这些基因多态性的原因。此外，NZW组外周血中中性粒细胞的数量明显高于NZB组，而且NZW组的中性粒细胞似乎比NZB组更活跃，从细胞大小来估计。此外，对抗CD3抗体刺激的脾T细胞的体外细胞因子分析表明，G-CSF能够增强Th2型细胞因子IL-4。根据这一结果，推测NZW型G-CSF基因的多态可能与高G-CSF水平有关，这可能是由于中性粒细胞数量和活性的增加而导致狼疮性肾炎的易感性，以及由于高Th2细胞因子的产生而上调IC的形成。

Systemic lupus erythematosus(SLE), a complex multigenic disease, is a typical antibody-mediated autoimmune disease characterized by production of autoantibodies against a variety of autoantigens and immune complex(IC)-type tissue inflammation, most prominently in the kidney. In SLE-prone (NZB x NZW) Fl mice, IC-type lupus nephritis more severe than parental NZB develop due to the contribution of susceptibility genes derived from both NZB and NZW strains. Our genome-wide scans to search for susceptibility genes for lupus nephritis in backcross mice of (NZB x NZW) Fl to NZB or NZW mice showed evidence that the NZB gene located in the vicinity of Clq and G-CSF receptor gene on chromosome 4 and NZW gene located in the vicinity of G-CSF gene on chromosome 11 are involved in severe nephritis. Sequence and functional analyses of Clq and G-CSF receptor genes revealed that the candidate gene on chromosome 4 seems to be Clq. Sequence analysis of G-CSF genes showed that there are sequence polymorphisms in 3' UTR region between NZB and NZW. Possibly due to these polymorphisms, G-CSF mRNA level and G-CSF production capacity by macrophages were significantly higher in NZW than in NZB. Furthermore, number of peripheral neutrophil was significantly higher in NZW than in NZB, and NZW neutrophil seemed to be more activated, estimated by enlarged cell size. In addition, in vitro cytokine analysis in anti-CD3 antibody-stimulated splenic T cells showed that G-CSF is able to enhance Th2-type cytokine, IL-4.Based on these findings, it was suggested that NZW-type polymorphic G-CSF gene possibly contribute to high G-CSF levels, which in turn contribute to the susceptibility to lupus nephritis due to the increase in neutrophil number and activity, and due to the up-regulation of IC-formation through the high level of Th2 cytokine production.