Kadowaki N, Amakawa R, Hayashi T, Akasaka T, Yabumoto K, Ohno H, Fukuhara S, Okuma M
Department of Internal Medicine, Faculty of Medicine, Kyoto University, Japan.
Leukemia. 1995 Jul;9(7):1139-43.
Previously, we reported the establishment of a human lymphoma cell line, FL-318, carrying a t(14;18)(q32;q21) chromosomal translocation. FL-318 cells had mu-heavy chain on the cell surface, while they expressed 'sterile' germ-line gamma transcripts, suggesting that the chromatin structure of the immunoglobulin heavy chain (IGH) locus was 'accessible' to class switch recombination. After several months of in vitro cell culture, we found a small population of FL-318 cells expressing the gamma-chain. Using a limiting dilution method, a mu-producing cell clone FL-318M, and gamma-producing FL-318G were isolated. Hybridization studies with various DNA probes from the IGH locus as well as the BCL2 gene demonstrated that the mu-constant gene was deleted on the functional IGH allele of FL-318G cells, and that the cells produced abundant productive gamma-chain messages. These studies indicated that FL-318 cells underwent spontaneous class switching during in vitro cell culture, unrelated to T cell interaction or antigenic stimulation.
此前，我们报道了携带t(14;18)(q32;q21)染色体易位的人淋巴瘤细胞系FL-318的建立。FL-318细胞在细胞表面有μ重链，同时表达“无功能的”种系γ转录本，这表明免疫球蛋白重链（IGH）基因座的染色质结构对于类别转换重组是“可及的”。经过数月的体外细胞培养后，我们发现一小群FL-318细胞表达γ链。采用有限稀释法，分离出产生μ链的细胞克隆FL-318M和产生γ链的FL-318G。用来自IGH基因座以及BCL2基因的各种DNA探针进行杂交研究表明，FL-318G细胞的功能性IGH等位基因上的μ恒定基因缺失，并且这些细胞产生了丰富的有功能的γ链信使。这些研究表明，FL-318细胞在体外细胞培养过程中发生了自发的类别转换，这与T细胞相互作用或抗原刺激无关。
