Klein Jan, Nikolaidis Nikolas
Department of Biology and Institute of Molecular Evolutionary Genetics, Pennsylvania State University, University Park, PA 16802, USA.
Proc Natl Acad Sci U S A. 2005 Jan 4;102(1):169-74. doi: 10.1073/pnas.0408480102. Epub 2004 Dec 23.
The antibody-based immune system (AIS) is one of many means by which organisms protect themselves against pathogens and parasites. The AIS is present in jawed vertebrates (gnathostomes) but absent in all other taxa, including jawless vertebrates (agnathans). We argue that the AIS has been assembled from elements that have primarily evolved to serve other functions and incorporated existing molecular cascades, resulting in the appearance of new organs and new types of cells. Some molecules serving other functions have been appropriated by the AIS, whereas others have been modified to serve new functions, either after the duplication of their encoding genes or through the acquisition of an additional function without gene duplication. A few molecules may have been created de novo. The deployment and integration of the ready-made elements gives the impression of a sudden origin of the AIS. In reality, however, the AIS is an example of an organ system that has evolved gradually through a series of small steps over an extended period.
基于抗体的免疫系统（AIS）是生物体抵御病原体和寄生虫的多种方式之一。AIS存在于有颌脊椎动物（gnathostomes）中，但在所有其他类群中都不存在，包括无颌脊椎动物（agnathans）。我们认为，AIS是由主要为其他功能而进化的元件组装而成，并整合了现有的分子级联反应，从而导致新器官和新细胞类型的出现。一些执行其他功能的分子被AIS所利用，而其他一些分子则在其编码基因复制后或通过在没有基因复制的情况下获得额外功能而被修饰以执行新功能。少数分子可能是从头产生的。现成元件的部署和整合给人一种AIS突然起源的印象。然而，实际上，AIS是一个器官系统的例子，它在很长一段时间内通过一系列小步骤逐渐进化而来。
