散发型高IgM综合征CD_(40)配体基因突变检测

Characterization of a novel mutation in the CD40 ligand gene in a patient with sporadic hyper IgM syndrome

目的揭示１例散发型高ＩｇＭ综合征（ＨＩＭ）患儿发病机制及其遗传类型，从而为其今后可能的基因治疗打下基础。方法用夹心酶联免疫吸附试验（ＥＬＩＳＡ）法检测患儿外周血单个核细胞分泌免疫球蛋白的能力；用单克隆抗体染色检测ＣＤ４０配体（ＣＤ４０Ｌ）表达情况；聚合酶链反应（ＰＣＲ）产物直接序列分析检测患儿ＣＤ４０Ｌ开放阅读框架基因突变。结果此例ＨＩＭ患儿Ｂ细胞体外刺激可产生ＩｇＧ，Ｔ细胞表面ＣＤ４０Ｌ染色阴性，序列分析发现６５４６５７位碱基缺失。结论患儿Ｂ细胞可能具有正常Ｉｇ分泌功能，Ｉｇ同种型转换障碍是由于其Ｔ细胞ＣＤ４０Ｌ基因缺失。

Objective To identify the inherited mode of sporadic hyper IgM syndrome (HIM) in a Chinese patient and to lay a foundation for the future gene therapy for the patients. Methods IgG, IgA, and IgM secretion by peripheral blood mononuclear cells in vitro was examined with enzyme linked immunosorbent assay. Ligand (CD 40 L) expression on activated T cells was detected by staining with CD 40 LmAb. Direct sequencing was used to identify the mutations on CD 40 L cDNA open reading frame. Results Costimulation of B cells in vitro from the sporadic HIM patient resulted in IgG production. CD 40 L expression was completely negative. Sequencing analysis showed a 4 base deletion (AGAT) at 654 657 in the patient′s CD 40 L open reading frame. Conclusion Failure of B cells to undergo immunoglobulin isotype switch in this case is a result of mutation on the CD 40 L gene in the activated T cells and B cells may have the ability to secrete IgG. This is the first case of HIGM with X linked inheritance diagnosed at a molecular level in China.