无颌脊椎动物具有替代的适应性免疫系统,其中抗原被富含亮氨酸重复序列(LRR)盒的组合组装产生的可变淋巴细胞受体(VLR)识别。三种类型的受体,VLRA,VLRB,和VLRC,之前已经确定。表达VLRA和VLRC的细胞是T细胞样,而表达VLRB的细胞是B细胞样的。这里,我们报道了七叶鱼中的两种类型的VLR,VLRD和VLRE,与VLRA和VLRC相关的系统发育。种系VLRD和VLRE基因的侧翼是39个用于装配成熟VLRD和VLRE的LRR盒,含有VLRA和VLRC基因的染色体盒也有助于VLRD和VLRE组装。VLRD和VLRE转录在三阴性(VLRA-/VLRB-/VLRC-)淋巴细胞群中最高,尽管在VLRA+和VLRC+群体中也可检测到。组织分布研究表明,七叶鱼VLRD和VLRE淋巴细胞包含T样亚谱系的细胞。
Jawless vertebrates possess an alternative adaptive immune system in which antigens are recognized by variable lymphocyte receptors (VLRs) generated by combinatorial assembly of leucine-rich repeat (LRR) cassettes. Three types of receptors, VLRA, VLRB, and VLRC, have been previously identified. VLRA- and VLRC-expressing cells are T cell-like, whereas VLRB-expressing cells are B cell-like. Here, we report two types of VLRs in lampreys, VLRD and VLRE, phylogenetically related to VLRA and VLRC. The germline VLRD and VLRE genes are flanked by 39 LRR cassettes used in the assembly of mature VLRD and VLRE, with cassettes from chromosomes containing the VLRA and VLRC genes also contributing to VLRD and VLRE assemblies. VLRD and VLRE transcription is highest in the triple-negative (VLRA-/VLRB-/VLRC-) population of lymphocytes, albeit also detectable in VLRA+ and VLRC+ populations. Tissue distribution studies suggest that lamprey VLRD+ and VLRE+ lymphocytes comprise T-like sublineages of cells.