Cannon John P, Haire Robert N, Litman Gary W
Immunology Program, H. Lee Moffitt Cancer Center and Research Institute, 12902 Magnolia Avenue, Tampa, FL 33612, USA.
Nat Immunol. 2002 Dec;3(12):1200-7. doi: 10.1038/ni849. Epub 2002 Nov 4.
The evolutionary origin of adaptive immune receptors is not understood below the phylogenetic level of the jawed vertebrates. We describe here a strategy for the selective cloning of cDNAs encoding secreted or transmembrane proteins that uses a bacterial plasmid (Amptrap) with a defective beta-lactamase gene. This method requires knowledge of only a single target motif that corresponds to as few as three amino acids; it was validated with major histocompatibility complex genes from a cartilaginous fish. Using this approach, we identified families of genes encoding secreted proteins with two diversified immunoglobulin-like variable (V) domains and a chitin-binding domain in amphioxus, a protochordate. Thus, multigenic families encoding diversified V regions exist in a species lacking an adaptive immune response.
在有颌脊椎动物的系统发育水平之下，适应性免疫受体的进化起源尚不清楚。我们在此描述一种用于选择性克隆编码分泌蛋白或跨膜蛋白的cDNA的策略，该策略使用带有缺陷β-内酰胺酶基因的细菌质粒（Amptrap）。此方法仅需了解一个对应于少至三个氨基酸的单一靶基序；它已通过软骨鱼类的主要组织相容性复合体基因得到验证。利用这种方法，我们在文昌鱼（一种原索动物）中鉴定出了编码具有两个多样化免疫球蛋白样可变（V）结构域和一个几丁质结合结构域的分泌蛋白的基因家族。因此，在缺乏适应性免疫反应的物种中存在编码多样化V区域的多基因家族。
