Pancer Zeev, Saha Nil Ratan, Kasamatsu Jun, Suzuki Takashi, Amemiya Chris T, Kasahara Masanori, Cooper Max D
Division of Developmental and Clinical Immunology, Department of Medicine, University of Alabama, Birmingham, AL 35294, USA.
Proc Natl Acad Sci U S A. 2005 Jun 28;102(26):9224-9. doi: 10.1073/pnas.0503792102. Epub 2005 Jun 17.
A previously uncharacterized type of variable lymphocyte receptors (VLR) was identified recently in the Sea lamprey. This jawless vertebrate generates an extensive VLR repertoire through differential insertion of neighboring diverse leucine-rich repeat (LRR) cassettes into an incomplete germ-line VLR gene. We report here VLR homologs from two additional lamprey species and the presence of two types of VLR genes in hagfish, the only other order of contemporary jawless vertebrates. As in the Sea lamprey, the incomplete hagfish germ-line VLR-A and -B genes are modified in lymphocyte-like cells to generate highly diverse repertoires of VLR-A and -B proteins via a presently undetermined mechanism. This jawless-fish mode of VLR diversification starkly contrasts with the rearrangement of Ig V(D)J gene segments used by all jawed vertebrates to produce diverse repertoires of T and B lymphocyte antigen receptors. The development of two very different strategies for receptor diversification at the dawn of vertebrate evolution approximately 500 million years ago attests to the fitness value of a lymphocyte-based system of anticipatory immunity.
最近在海七鳃鳗中发现了一种以前未被描述的可变淋巴细胞受体（VLR）类型。这种无颌脊椎动物通过将相邻的不同富含亮氨酸重复序列（LRR）盒差异插入到一个不完整的种系VLR基因中，产生了广泛的VLR库。我们在此报告了另外两种七鳃鳗物种的VLR同源物，以及盲鳗（当代唯一的另一目无颌脊椎动物）中两种类型的VLR基因的存在。与海七鳃鳗一样，不完整的盲鳗种系VLR-A和-B基因在类淋巴细胞中被修饰，通过目前尚未确定的机制产生高度多样化的VLR-A和-B蛋白库。这种无颌鱼类的VLR多样化模式与所有有颌脊椎动物用于产生多样化的T和B淋巴细胞抗原受体库的Ig V（D）J基因片段重排形成鲜明对比。大约5亿年前在脊椎动物进化初期出现的两种截然不同的受体多样化策略的发展，证明了基于淋巴细胞的预期免疫系统的适应性价值。
