规模化养殖大西洋鳕鱼是一些水产专家的梦想，但苦于细菌感染等问题难以成功。挪威研究人员的一项新发现可能帮助消除这个障碍，他们通过基因组测序发现，大西洋鳕鱼的免疫系统非常独特。
挪威奥斯陆大学的研究人员最近在英国《自然》杂志网络版上发表论文说，大西洋鳕鱼缺少一些对脊椎动物非常重要的基因。
这种现象在有颌类脊椎动物中还是头一次发现，将增进人们对脊椎动物免疫系统进化历程及人类免疫力的理解，还可帮助设计适合大西洋鳕鱼的新型疫苗。
有颌类脊椎动物指有着上、下颌的脊椎动物，除了一些原始种类，现存脊椎动物绝大部分都是有颌的。
研究发现，大西洋鳕鱼的基因组中缺少一组名叫“主要组织相容性复合体Ⅱ”（MHC Ⅱ）的基因，以及与这组基因有密切关系的另外两组基因。这三组基因是多数脊椎动物后天免疫系统的重要组成部分。
组织中有细菌等病原体侵入时，MHC Ⅱ基因将病原体的碎片“提交”给免疫细胞，激发免疫反应。曾有研究发现，缺少MHC Ⅱ基因的实验鼠有免疫缺陷，会患上严重疾病。
与一般脊椎动物相比，大西洋鳕鱼对免疫系统其他一些部分的依赖更重，这对MHC Ⅱ及相关基因的缺失起到了一定的补偿作用，使它们能正常生存。
研究人员猜测，大西洋鳕鱼可能在有着独特病原体组合的深水环境中进化，从而获得了独特的免疫系统。(生物谷 Bioon.com)
doi:10.1038/nature10342
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The genome sequence of Atlantic cod reveals a unique immune system
Bastiaan Star; Alexander J. Nederbragt; Sissel Jentoft; Unni Grimholt; Martin Malmstrøm; Tone F. Gregers; Trine B. Rounge; Jonas Paulsen; Monica H. Solbakken; Animesh Sharma; Ola F. Wetten; Anders Lanzén; Roger Winer; James Knight; Jan-Hinnerk Vogel; Bronwen Aken; Øivind Andersen; Karin Lagesen; Ave Tooming-Klunderud; Rolf B. Edvardsen; Kirubakaran G. Tina; Mari Espelund; Chirag Nepal; Christopher Previti; Bård Ove Karlsen; Truls Moum; Morten Skage; Paul R. Berg;
Atlantic cod (Gadus morhua) is a large, cold-adapted teleost that sustains long-standing commercial fisheries and incipient aquaculture1, 2. Here we present the genome sequence of Atlantic cod, showing evidence for complex thermal adaptations in its haemoglobin gene cluster and an unusual immune architecture compared to other sequenced vertebrates. The genome assembly was obtained exclusively by 454 sequencing of shotgun and paired-end libraries, and automated annotation identified 22,154 genes. The major histocompatibility complex (MHC) II is a conserved feature of the adaptive immune system of jawed vertebrates3, 4, but we show that Atlantic cod has lost the genes for MHC II, CD4 and invariant chain (Ii) that are essential for the function of this pathway. Nevertheless, Atlantic cod is not exceptionally susceptible to disease under natural conditions5. We find a highly expanded number of MHC I genes and a unique composition of its Toll-like receptor (TLR) families. This indicates how the Atlantic cod immune system has evolved compensatory mechanisms in both adaptive and innate immunity in the absence of MHC II. These observations affect fundamental assumptions about the evolution of the adaptive immune system and its components in vertebrates.
