急性B淋巴细胞白血病免疫球蛋白重链可变区的细胞毒T淋巴细胞识别表位  

Epitopes recognized by cytotoxic T lymphocytes in immunoglobulin heavy chain variable regions expressed by B-cell acute lymphoblastic leukemia

作　　者：刘英[1] 朱平[2] 胡亚美[3] 

机构地区：[1]解放军总医院小儿内科,北京100853 [2]北京大学第一医院 [3]首都医科大学附属北京儿童医院

出　　处：《中华肿瘤杂志》2005年第2期106-110,共5页Chinese Journal of Oncology

基　　金：北京市自然科学基金资助项目 (70 3 2 0 2 8)

摘　　要：目的　分析儿童急性B淋巴细胞白血病 (B ALL)细胞免疫球蛋白重链可变区 (IgHV)的基因特征 ,确定IgHV的细胞毒T淋巴细胞 (CTL)识别表位。方法　PCR扩增 37例儿童B ALL的 7个IgHV基因家族 ,PCR产物直接测序 ,利用生物信息资源 ,分析所得序列的特征并预测B ALL细胞IgHV上与HLA A 0 2 0 1分子结合的九肽。合成预测九肽QLVQSGAEV ,进行T B杂交瘤细胞系 (T2 )结合实验 ,用荷肽抗原呈递细胞 ,反复刺激HLA A 0 2 0 1正常供者外周血中肽特异性CD8+ T细胞的扩增。结果　 37例B ALL均检测到IgHV基因 ,经PCR产物测序 ,得到 4 0份IgHV基因序列 ,它们优先利用基因片段VH4 34(12 .5 % )和VH4 5 9(10 .0 % )。B ALL细胞的IgHV基因利用D7 2 7片段的频率 (15 .4 % )和在DJH结合区缺乏非编码核苷酸的频率 (2 0 .0 % ) ,均明显高于正常成人外周血淋巴细胞的IgHV基因。 17.5 %的序列含有不到 2 %的替代突变。从 4 0份B ALL细胞的IgHV序列 ,预测出 12条与HLA A 0 2 0 1分子有高亲和力的九肽 ,10条 (83.0 % )位于框架 1和 3区。合成九肽QLVQSGAEV使T2细胞表面HLA A 0 2 0 1分子的表达强度提高 1.6倍。HLA A 0 2 0 1正常供者外周血中的QLVQSGAEV特异性CD8+ T细胞 ,在荷肽抗原呈递细胞的重复刺激下 ,由 2轮刺激后的 1.6 %?Objective To clone IgHV genes from childhood B ALL cells and identify CTL epitopes deduced from IgHV gene. Methods Seven IgHV gene families were respectively amplified by PCR and directly sequenced for 37 childhood B ALL cases. Bioinformatics were applied for analyzing characteristics of sequences available and predicting HLA A*0201 molecule binding nonapeptides derived from IgHV. The predicted nonapeptide QLVQSGAEV was synthesized and its binding affinity to T2 cells determined. CD8 + T cells from a healthy HLA A*0201 + donor peripheral blood were stimulated repeatedly with QLVQSGAEV loaded antigen presenting cells. Results IgHV gene rearrangements were identified in 37 B ALL. Forty IgHV gene sequences available preferentially utilized V H 4 59 and V H 4 34 gene segments. Increased frequency(15.4%)of D7 27 in B ALL IgHV was found compared to that reported for adult PBLs(P=0.02); 20.0% DJ H junctions in B ALL lacked non encoding nucleotides, a frequency higher than that reported for adult PBLs (P=0.02). 17.5% B ALL IgHV contained <2% replacement mutations. Forty B ALL IgHV sequences acquired 12 high HLA A*0201 binding nonapeptides , 10 (83.0%) peptides were located in frame region (FR)1 and 3. The synthesized peptide QLVQSGAEV up regulated HLA A*0201 expression 1.63 fold on the surface of T2 cells. The frequency of QLVQSGAEV specific CD8 + T cells in a healthy HLA A*0201 + donor peripheral blood increased from 1.6% and 82.6% after two round and 3 round stimulations,respectively. Conclusion IgHV genes in childhood B ALL are of germline characteristics. Their heavy chain framework regions contain HLA A*0201 binding nonapeptides. These peptides are capable of inducing specific CD8 + T cells to activate and proliferate.

关 键 词：HLA-A CD8^+T细胞 急性B淋巴细胞白血病 表位 细胞毒T淋巴细胞 基因 正常供者 PCR产物 序列 重链可变区 

分 类 号：R733.7[医药卫生—肿瘤]