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

系统性红斑狼疮（systemic lupus erythematosus，SLE）是一种复杂的多基因疾病，是典型的抗体介导的自身免疫性疾病，其特征在于产生针对多种自身抗原的自身抗体和免疫复合物（immune complex，IC）型组织炎症，最突出的是肾脏。在SLE易感（NZB x NZW）F1小鼠中，由于源自NZB和NZW菌株的易感基因的贡献，IC型狼疮肾炎比亲本NZB更严重。我们在（NZB x NZW）F1与NZB或NZW小鼠的回交小鼠中进行全基因组扫描以寻找狼疮性肾炎的易感基因，发现位于4号染色体上Clq和G-CSF受体基因附近的NZB基因和位于11号染色体上G-CSF基因附近的NZW基因参与严重肾炎。Clq和G-CSF受体基因的序列和功能分析显示，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在3' UTR区存在序列多态性。可能是由于这些多态性，G-CSF mRNA水平和G-CSF生产能力的巨噬细胞显着高于NZB在NZW。此外，外周中性粒细胞的数量显着高于NZB，NZW中性粒细胞似乎更活跃，估计扩大细胞大小。此外，在抗CD 3抗体刺激的脾T细胞中，体外细胞因子分析显示G-CSF能够增强Th 2型细胞因子IL-4。基于这些发现，提示NZW型多态性G-CSF基因可能有助于高G-CSF水平，而高G-CSF水平反过来又有助于狼疮肾炎的易感性，这是由于中性粒细胞数量和活性增加，以及由于通过高水平的Th 2细胞因子产生而上调IC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.