阿尔茨海默病患者血清自身抗Aβ抗体亲和力的测定及意义

Measurement of avidity of serum autoantiboldies to Aβs and its significance in patients with Alzheimer＇s disease

目的探讨阿尔茨海默病（AD）患者自身抗Aβ抗体亲和力情况。方法选择AD患者、正常中年人和正常老年人各20例，通过间接ELISA法结合硫氰酸盐洗脱检测各组血清抗Aβ抗体相对亲和力。结果AD组血清抗Aβ抗体亲和力值为1．6（四分位数范围1．15-2．05），明显低于正常老年组[2．45（四分位数范围1．75-3．08）]，差异有统计学意义（P=0.020）；正常中年组[2．35（四分位数范围1．35-3．05）]和正常老年组间差异无统计学意义（P=0.220）。根据对硫氰酸盐洗脱耐受情况将抗Aβ多克隆抗体组成分为低、中、高亲和力亚群，AD组低亲和力抗体为13％（四分位数范围5％～18％），明显高于正常老年组[5％（四分位数范围3％～10％）]，差异有统计学意义（P=0．000）；而AD组高亲和力抗体为15％（四分位数范围5％-24％），明显低于正常老年组[35％（四分位数范围26％-44％）]，差异有统计学意义（P=0.006）。结论AD患者血清自身抗Aβ抗体亲和力低于正常，抗Aβ多克隆抗体组成成份发生变化，低亲和力抗体亚群比例明显升高，推测可能是B细胞不完全免疫耐受在其中发挥着重要作用。

Objective To measure the avidity of serum autoanfibodies to Aβs in patients with Alzheimer＇s disease （AD）. Methods Enzyme-linked immunosorbent assay （ELISA） combined with thiocyanate elution technique was employed to detect the avidity of serum autoantibodies to Aβs in patients with AD, middle-aged and healthy elderly adults （n=20）. Results The avidity of serum autoantibodies to Aβs in patients with AD （avidity index, 1.6 [1.15 to 2.05]） was significantly lower as compared with that in healthy elderly subjects （avidity index, 2.45 [1.75 to 3.08]） （P=0.020） and no significant difference was showed in the avidity of autoanfibodies to Aβs between the elderly and middle-aged healthy adults （P=0.221）. An evident shift to the low section was observed in patients with AD in the avidity distribution histogram. The proportion of low affinity antibodies was significantly higher in patients with AD （13% [5% to 18%]） than that in healthy elderly subjects （5% [3% to 10%]） （P = 0.000）, and the proportion of high affinity antibodies was significantly lower in patients with AD （15% [5% to 24%]） than that in elderly adults （35% [26% to 44%]） （P=0.006）. Conclusion Low avidity of autoantibodies to Aβs is confirmed in AD patients. Patients with AD show a significantly high proportion of low affinity antibodies than normal adults and the components of polyclonal antibodies change in patients with AD, probably resulting from incomplete immune tolerance of B cells.