七鰓鰻和八目鰻（最后的無頜類脊椎動物）之所以吸引免疫學家注意,，是因為它們的適應性免疫系統(tǒng)在靈活性上可與人類的相媲美,。在人類身上,，每個淋巴細胞表達針對某一種抗原的預期性受體，由可變的、多樣的連接片段構(gòu)成,。無頜類脊椎動物利用由“富含亮氨酸重復序列”的蛋白片段組成的可變淋巴細胞受體,，并有一個不可變的柄系在淋巴細胞表面上。
對海生七鰓鰻所做的新的研究工作顯示了更多與人類相似的地方：它們有一個分成不同腔室的適應性免疫系統(tǒng),，含有與哺乳動物適應性免疫系統(tǒng)中分泌細胞因子的T-細胞及分泌抗體的B-細胞相似的細胞,。這表明，淋巴細胞分化沿類似T-細胞和B-細胞系方向上所發(fā)生的分歧在演化上出現(xiàn)的時間要比人們以前所認為的早得多,，因而它們的系統(tǒng)不是我們?nèi)祟愖约好庖呦到y(tǒng)的一個先驅(qū),，就是同我們自己的免疫系統(tǒng)并行演化的。（生物谷Bioon.com）
生物谷推薦原始出處：
Nature 459, 796-801 (11 June 2009) | doi:10.1038/nature08068
Dual nature of the adaptive immune system in lampreys
Peng Guo1,2, Masayuki Hirano1,2, Brantley R. Herrin1,2, Jianxu Li1, Cuiling Yu1, Andrea Sadlonova1 & Max D. Cooper1
1 Emory Vaccine Center and Department of Pathology and Laboratory Medicine, Emory University, 1462 Clifton Road North-East, Atlanta, Georgia 30322, USA
2 These authors contributed equally to this work.
Jawless vertebrates use variable lymphocyte receptors (VLR) comprised of leucine-rich-repeat (LRR) segments as counterparts of the immunoglobulin-based receptors that jawed vertebrates use for antigen recognition. Highly diverse VLR genes are somatically assembled by the insertion of variable LRR sequences into incomplete germline VLRA and VLRB genes. Here we show that in sea lampreys (Petromyzon marinus) VLRA and VLRB anticipatory receptors are expressed by separate lymphocyte populations by monoallelic VLRA or VLRB assembly, together with expression of cytosine deaminase 1 (CDA1) or 2 (CDA2), respectively. Distinctive gene expression profiles for VLRA+ and VLRB+ lymphocytes resemble those of mammalian T and B cells. Although both the VLRA and the VLRB cells proliferate in response to antigenic stimulation, only the VLRB lymphocytes bind native antigens and differentiate into VLR antibody-secreting cells. Conversely, VLRA lymphocytes respond preferentially to a classical T-cell mitogen and upregulate the expression of the pro-inflammatory cytokine genes interleukin-17 (IL-17) and macrophage migration inhibitory factor (MIF). The finding of T-like and B-like lymphocytes in lampreys offers new insight into the evolution of adaptive immunity.
