Magor B G, De Tomaso A, Rinkevich B, Weissman I L
Hopkins Marine Station, Stanford University, Pacific Grove, California, USA.
Immunol Rev. 1999 Feb;167:69-79. doi: 10.1111/j.1600-065x.1999.tb01383.x.
The MHC molecules have been historically perceived as transplantation antigens, though it is now recognized that their primary, if not sole, role is in eliminating parasites and in surveillance and clearance of aberrant self. Indeed, pregnancy in mammals would represent the closest to a natural transplantation process that occurs in vertebrates. However, among the immediate ancestors to the vertebrates, natural intraspecific allorecognition processes are common. Among members of the colonial tunicate Botryllus schlosseri, two individuals that share a single allele of the highly polymorphic fusibility/histocompatibility (Fu/HC) locus are able to fuse with one another. Could this Fu/HC be related to the MHC such that the MHC really did have its origins as a transplantation antigen? Presently we review the genetics and biology of natural transplantation processes in colonial tunicates, comparing it with allorecognition as mediated through the vertebrate T-cell receptor, killer cell inhibitory receptor/Ly49, and MHC. Experimental approaches to determining if the molecules regulating allorecognition in tunicates have any ancestral relationship to the vertebrate MHC are discussed, as is a genomic approach to isolating novel mediators of allorecognition. We also explore the biological basis for allorecognition in colonial tunicates and recent work that highlights the costs of not maintaining a system for allorecognition.
历史上，MHC分子一直被视为移植抗原，不过现在人们认识到，其主要作用（即便不是唯一作用）是清除寄生虫以及监测和清除异常自身物质。事实上，哺乳动物的妊娠可说是脊椎动物中最接近自然移植过程的情况。然而，在脊椎动物的直系祖先中，自然种内异体识别过程很常见。在群体被囊动物博特瑞虫（Botryllus schlosseri）的成员中，共享高度多态的融合性/组织相容性（Fu/HC）位点单一等位基因的两个个体能够相互融合。这个Fu/HC会与MHC有关吗，以至于MHC真的起源于移植抗原？目前，我们综述群体被囊动物自然移植过程的遗传学和生物学，将其与通过脊椎动物T细胞受体、杀伤细胞抑制受体/Ly49和MHC介导的异体识别进行比较。讨论了确定调节被囊动物异体识别的分子是否与脊椎动物MHC存在任何祖先关系的实验方法，以及分离异体识别新介质的基因组方法。我们还探讨了群体被囊动物异体识别的生物学基础以及近期强调不维持异体识别系统的代价的研究工作。
