红细胞补体受体1基因多态性与特发性肺纤维化易感性的关系

Association between genetic polymorphism of erythrocyte CR1 and the susceptibility of idiopathic pulmonary fibrosis

目的探讨红细胞补体受体1（CR1）密度基因多态性及CR1基因A3650G位点多态性与特发性肺纤维化（IPF）易感性的关系，CR1的HindⅢ密度相关基因组多态性与红细胞膜上CR1数量表达水平的关系。方法选择2009年11月至2010年12月在河北医科大学第二医院确诊为特发性肺纤维化汉族患者64例（IPF组）及54名同期河北医科大学第二医院健康汉族体检者作为健康对照组。应用聚合酶链反应-限制性片段长度多态性（PCR—RFLP）及聚合酶链反应（PCR）检测两组CR1的HindⅢ密度相关基因组多态性以及CR1基因A3650G多态位点的基因型；采用流式细胞术检测CR1在红细胞膜上的数量表达水平。结果CR1HindⅢ密度相关基因基因型HH型、HL型和LL型在IPF组的分布频率分别为32．8％（21／64）、46．9％（30／64）和20．3％（13／64），在健康对照组分布频率分别为72．2％（39／54）、25．9％（14／54）和1．9％（1／54），差异有统计学意义（x2=15．516，P〈0．05）。IPF组与健康对照组HL＋LL基因型优势比OR值为5．32（x2=18．20，P〈0．05）。CR1基因A3650G位点的等位基因频率在IPF患者和健康对照组之间比较，总体分布差异无统计学意义（X2=1．094，P〉0．05）。CR1在IPF组红细胞上的平均荧光强度为13．46±3．86，与健康对照组（24．33±3．84）比较，差异有统计学意义（t=15．288，P〈0．05）。两组CR1基因HindⅢ-RFLP高表达型的红细胞CR1数量表达水平高于中表达型（t=9．973，P〈0．05），中表达型高于低表达型（t=4．359，P〈0．05）。IPF组CRI基因HindⅢ—RFLP高表达型、中表达型、低表达型的红细胞CR1数量表达水平均低于健康对照人群（均P〈0．05）。结论红细胞CR1数量表达水平既受CR1基因HindⅢ密度相关基因组多态性遗传控制又受后天因素的影响。CR1基因HL型和LL型人群可能是特发性肺纤维化的易感人群，携带L等位基因的个体存在对特发性肺纤维化的易感性。

Objective To explore the association between the erythrocyte CR1 genomic density polymorphism, A3650G site polymorphism and the susceptibility of idiopathic pulmonary fibrosis （IPF）; and to investigate the correlation between the Hind Ⅲ density polymorphism of CR1 gene and the quantitative levels of E-CRI in IPF patients. Methods Blood samples from IPF patients （n = 64 ） and ethnically matched healthy controls （ n = 54 ） were taken from a population-based case-control association study. Polymerase chain reaction-restriction fragment length polymorphism （PCR-RFLP） was performed to identify the genotype of the HindⅢ restriction fragment length polymorphism of CR1 gene and SNP A3650G in two groups. Quantitative expression of CR1 on RBC membrane surface was detected by flow cytometry. Results Thegenotype frequencies of HH, HL and LL were 32.8 % （21/64）, 46.9 % （30/64） and 20.3 % （13/64） respectively in the IPF group, and 72.2 % （39/54）, 25.9 % （14/54） and 1.9 % （1/54） respectively in the controls. The distribution of geuotype between the two groups was significantly different （X2 = 15. 516, P 〈 0. 05）. HL ＋ LL genotype for the Hind Ⅲ polymorphism was more common in patients with IPF compared to the controls with an OR =5.32（X2 = 18.20, P 〈0.05）. Compared the allele frequency of A3650G sites in the IPF group with that in the control group, there was no difference from distribution in the two groups （ X2 = 1. 094, P 〉 O. 05 ）. The mean CR1/E numbers observed in the IPF patients was 13.46 - 3.86, and the mean CR1/E in normal individuals was 24. 33 ＋- 3.84（ t = 15. 288, P 〈 0. 05 vs IPF group）. The levels of E-CR1 in both IPF patients and healthy controls HH genotype for E-CR1 Hind Ⅲ-RFLP were significantly higher than HL genotype for E-CR1 HindⅢ-RFLP（t = 9. 973, P 〈 0. 05 ）, and the levels of E-CR1 in both groups HL genotype for E-CR1 Hindm-RFLP were significantly higher than LL genotype for E-CR1 HindⅢ-RFLP（t =9. 973, P 〈0. 05）. The levels of HH, HL and LL genotypes for E-CR1 Hind Ⅲ-RFLP in the IPF group were significantly lower than those in the control group, respectively （P 〈 0. 05, on average）. Conclusion The quantitative levels of CR1 on erythrocyte membrane was not only determined by the genetic background of E-CR1 Hind Ⅲ-RFLP but also by the acquired predisposition. HL and LL genotypes of CR1 gene may be associated with IPF, and as a result individuals carrying the L allele might be a susceptible population for IPF.