Thomas E. Starzl Transplantation Institute; Departments of Surgery and Immunology; University of Pittsburgh School of Medicine; Pittsburgh, Pennsylvania USA.
Organogenesis. 2008 Oct;4(4):236-40. doi: 10.4161/org.4.4.7151.
The presence of highly specific histocompatibility reactions in colonial marine invertebrates that lack adaptive immune systems (such as the sponges, cnidarians, bryozoans and ascidians) provides a unique opportunity to investigate the evolutionary roots of allorecognition and to explore whether homologous innate recognition systems exist in vertebrates. Conspecific interactions among adult animals in these groups are regulated by highly specific allorecognition systems that restrict somatic fusion to self or close kin. In Hydractinia (Cnidaria:Hydrozoa), fusion/rejection responses are controlled by two linked genetic loci. Alleles at each locus are co-dominantly inherited. Colonies fuse if they share at least one haplotype, reject if they share no haplotypes, and display transitory fusion if they share only one allele in a haplotype-a pattern that echoes natural killer cell responses in mice and humans. Allorecognition in Hydractinia and other marine invertebrates serves as a safeguard against stem cell or germline parasitism thus, limiting chimerism to closely related individuals. These animals fail to become tolerant even if exposed during early development to cells from a histoincompatible individual. Detailed analysis of the structure and function of molecules responsible for allorecognition in basal marine invertebrates could provide clues to the innate mechanisms by which higher animals respond to organ and cell allografts, including embryonic tissues.
在缺乏适应性免疫系统的海洋无脊椎动物（如海绵、刺胞动物、苔藓动物和海鞘）中存在高度特异性的组织相容性反应，这为研究同种异体识别的进化根源以及探索同源先天识别系统是否存在于脊椎动物中提供了独特的机会。这些群体中成年动物之间的同种相互作用受高度特异性同种异体识别系统的调节，该系统将体细胞融合限制在自身或近亲之间。在水螅（刺胞动物：水螅纲）中，融合/排斥反应受两个连锁的遗传位点控制。每个位点的等位基因都是共显性遗传的。如果它们共享至少一个单倍型，则殖民地融合；如果它们不共享任何单倍型，则排斥；如果它们仅在一个单倍型中共享一个等位基因，则显示暂时融合——这种模式与小鼠和人类自然杀伤细胞反应相呼应。水螅和其他海洋无脊椎动物的同种异体识别作为防止干细胞或生殖系寄生的保护措施，从而将嵌合体限制在密切相关的个体中。这些动物即使在早期发育过程中暴露于来自组织不相容个体的细胞，也无法变得耐受。对负责基础海洋无脊椎动物同种异体识别的分子的结构和功能进行详细分析，可以为高等动物对器官和细胞同种异体移植物（包括胚胎组织）做出反应的先天机制提供线索。
