1例新发TYK2基因突变患儿临床分子特征及免疫学表型研究

Clinical and immunological characteristics of a newly identified TYK2-mutant patient

目的报道1例新发TYK2基因突变患儿的临床特征、诊治经过及免疫学表型,同时总结文献已报道的9例TYK2缺陷患者资料,期望促进对本病的早期识别及规范治疗。方法总结临床资料,采用Sanger测序验证本例患儿二代测序报告所示突变位点,预测错义突变对TYK2蛋白结构及功能的影响;利用蛋白印迹法检测TYK2蛋白表达,流式细胞术检测淋巴细胞各亚群分布以及NK细胞表达CD107a水平。结果此前报道的TYK2缺陷患者临床表现多变,以卡介苗病、反复感染、湿疹为主,部分可伴有血清IgE水平升高或嗜酸性粒细胞增多。因此是否将本病归为高IgE综合征存在很大争议。本例患儿TYK2基因发生复合杂合突变(c.3041T>C,c.1253C>A),TYK2蛋白表达缺失,血清IgE水平正常,但外周血嗜酸性粒细胞比例增高;外周血CD4^+T细胞、初始CD4^+T细胞比例减少,过渡型B细胞、中心记忆CD4^+T细胞及效应记忆CD4^+T细胞比例升高;Tfh细胞比例稍增高,Tfh1比例增高,Tfh2与Tfh17比例稍降低;同时,患儿NK细胞表达CD107a水平下降。结论本研究报道了TYK2基因新发突变1例,对于卡介苗接种后出现异常反应(特别是严重的卡介苗病)、有反复胞内菌及病毒感染、湿疹史的患儿应疑诊此病,二代测序有助于快速明确诊断。此例患儿外周血CD4^+T细胞比例下降,且各亚群分布异常,NK细胞表达CD107a水平下降,具体机制需进一步明确。

TYK2 deficiency is a rare primary immunodeficiency caused by mutations in the TYK2 gene.In the present study,we reported a newly identified TYK2-mutant patient,and analyzed the clinical data about all 9 previously reported TYK2-deficient patients with an aim of providing more reliable information to clinicians in China.Sanger sequencing of TYK2 gene,analysis of TYK2 protein expression by Western blotting,distribution of lymphocyte subsets and CD107 a expression of NK cells by FCM have been taken for diagnosis and immunological evaluation.Data showed that our patient carried a compound heterozygous mutation in TYK2 gene(c.3041 T>C,c.1253 C>A)with undetectable expression of TYK2 protein.FCM showed a lower percentage of total CD4^+T cells and naive CD4^+T cells,and a higher percentage of transitional B cells,CD4 CM,and CD4 EM.In addition,the patient demonstrated a slightly higher percentage of Tfh,with more Tfh1,and less Tfh2,Tfh17.CD107a expression by NK cells was also lower in our case.In summary,for patients who suffered adverse reaction after BCG vaccination,recurrent intracellular bacteria or virus infections and eczema,TYK2 deficiency should be considered.High-throughput sequencing would be helpful for quick diagnosis.Our patient also demonstrated abnormal distribution of CD4^+T cells and its subsets,as well as decreased CD107a expression of NK cells,whose underlying mechanisms need further studies.