儿童急性B淋巴细胞白血病免疫球蛋白重链可变区基因的分子特征  

Characteristics of immunoglobulin heavy chain variable region genes in childhood B-cell acute lymphoblastic leukemia

作　　者：刘英[1] 朱平[1] 胡亚美[2] 

机构地区：[1]北京大学第一医院 [2]首都医科大学附属北京儿童医院血液中心

出　　处：《中华血液学杂志》2004年第1期8-12,共5页Chinese Journal of Hematology

基　　金：国家自然科学基金资助项目 (3 9970 3 13 ) ;北京市自然科学基金资助项目 (70 3 2 0 2 8)

摘　　要：目的　探讨儿童急性B淋巴细胞白血病 (B ALL)的起源及其免疫球蛋白重链可变区(IgHV)上可被细胞毒性T淋巴细胞 (CTL)识别的表位 (epitope)。方法　PCR扩增 10 8例儿童ALL的 7个IgHV基因家族 ;PCR产物直接测序并翻译成氨基酸序列 ;利用生物信息资源分析B ALLIgHV基因重排类型、胚系基因片段利用及体细胞突变情况 ,并预测CTL细胞识别的表位。结果　 6 6 %的ALL患儿检测到IgHV基因重排 ,其中单等位基因重排 37例 (5 2 .1% ) ,双等位基因重排 2 6例 (36 .6 % ) ,寡克隆基因重排 8例 (11.3% )。 4 0份B ALLIgHV基因序列中 ,不含终止密码子的读码框内 (inframe)重排 8份 (2 0 0 % )。重排利用最多的VH 家族为VH3、VH4和VH1,占 75 % ;VH4 5 9和VH4 34是VH4家族中利用频率最高的片段。优先利用的D家族为D3(35 .9% )和D2 (2 8.2 % ) ,D7 2 7的利用率 (15 .4 % )明显高于正常外周血淋巴细胞 (P =0 .0 2 )。JH6是B ALL利用最多的JH 基因片段 (47.5 % ) ,JH4 (2 7.5 % )次之。2 0 %的B ALL在DJH 连接区缺乏N核苷酸的插入 ,高于正常外周血淋巴细胞 (P =0 .0 2 )。 17.5 %B ALLIgHV基因发生替代突变 ,突变碱基散布于IgHV全长 ,互补决定区替代突变与静寂突变的比例≤1。 2 6例B ALLIgHV的HLA Ⅰ类分子结合肽 80Objective To investigate the origin of childhood B-cell acute lymphoblastic leukemia (B-ALL) and its epitopes recognized by cytotoxic T lymphocytes(CTL) in immunoglobulin heavy chain variable region(IgHV). Methods Seven IgHV gene families were respectively amplified by PCR and directly sequenced in 108 childhood ALL. The amino acid sequences were deducted from sequenced nucleotides. Bioinformatics was applied to analyses of recombination patterns,somatic mutations and germline gene segments usage,and to prediction of epitopes recognized by CTL. Results IgHV gene rearrangements were identified in 66% of the cases,including 37(52.1%)monoallelic rearrangements,26(36.6%)biallelic rearrangements and 8(11.3%)oligoclonal rearrangements. Among the obtained 40 B-ALL IgHV gene sequences,8(20.0%) were in frame rearrangements without stop codons. V_H3(11/40),V_H4(11/40)and V_H1(8/40)amounted to 75% rearranged V_H families. V_H4-59 and V_H4-34 were the most frequently rearranged V_H4 family gene segments. Usage of D2 and D3 families was most prominent(35.9% and 28.2%, respectively). Increased frequency of D7-27 (15.4%)was found as compared to that of normal peripheral B lymphocytes(P =0.02). J_H6 was found in 47.5% rearrangements followed by J_H4(27.5%). 8/40(20.0%) DJ_H junctions lacked N nucleotides,which was higher than that reported for normal peripheral B lymphocytes(P =0.02). 17.5% B-ALL IgHV contained scattered replacement mutations with replacement(R) to silent(S) substitution ratio(R/S ratio) ≤1 in complementarity determining region(CDR). Above 80% potential HLA class I molecule-binding peptides were derived from framework regions of immunoglobulin heavy chains in 26 B-ALL cases and 1～2 peptides of the same IgHV family were shared by B-ALL. Conclusion B-ALL originated from progenitor or precursor B lymphocytes. B-ALL IgHV genes are of germline characteristics. Potential T cell epitopes were derived from framework regions 1 and 3 of immunoglobulin heavy chain in B-ALL.

关 键 词：儿童 急性B淋巴细胞白血病 免疫球蛋白重链可变区基因 T淋巴细胞 PCR 外周血 生物信息资源 

分 类 号：R733.7[医药卫生—肿瘤]