Leukocyte immune-type receptors (LITRs) are a large family of immunoregulatory receptor-types originally identified in the channel catfish (Ictalurus punctatus (Ip)LITRs). Phylogenetic analyses of LITRs show that they share distant evolutionary relationships with important mammalian immunoregulatory receptors belonging to the Fc receptors family and the leukocyte receptor complex (LRC), but their syntenic relationships with these immunoglobulin superfamily members have not been investigated. To further examine the possible evolutionary connections between teleost LITRs and various mammalian immunoregulatory receptor-types, we surveyed the genomic databases of representative vertebrate taxa and our results show that teleost LITRs generally exist in large genomic clusters, which are linked to vangl2, arhgef11, and slam family genes, features that are also shared by amphibian and mammalian Fc receptor-like molecules (FCRLs). Moreover, detailed phylogenetic comparisons between the individual Ig-like domains of LITRs and mammalian FCRLs shows that these receptors share related Ig-like domains indicative of their common ancestry. However, contrary to our previous reports, no supportive evidence for phylogenetic relationships between the Ig-like domains of LITRs with the Ig-like domains of LRC-encoded mammalian immunoregulatory receptors was found. We also identified an LRC-like region in the zebrafish genome, but no expanded litr-related genes were located in this region. Similarly, no lilr-related genes were found in spotted gar, a representative basal ray-finned fish. Finally, two distantly related fcrls and an LRC-like gene were identified in the elephant shark genome, suggesting that the loss of an immunoregulatory receptor-containing LRC region may be unique to ray-finned fish.

白细胞免疫型受体 (LITRs) 是一大类免疫调节受体类型，最初在沟鲶 ( Ictalurus punctatus (Ip)LITRs) 中发现。LITR 的系统发育分析表明，它们与属于 Fc 受体家族和白细胞受体复合物 (LRC) 的重要哺乳动物免疫调节受体具有远距离的进化关系，但尚未研究它们与这些免疫球蛋白超家族成员的同线关系。为了进一步研究硬骨鱼类LITRs和各种哺乳动物的免疫调节受体类型之间的可能的进化联系，我们调查了代表脊椎动物类群的基因组数据库，我们的结果表明，硬骨鱼类LITRs一般在大型基因组群，这两篇文章存在VANGL2、arhgef11和slam家族基因，这些特征也是两栖动物和哺乳动物 Fc 受体样分子 (FCRL) 共有的。此外，LITR 和哺乳动物 FCRL 的单个 Ig 样结构域之间的详细系统发育比较表明，这些受体共享相关的 Ig 样结构域，表明它们的共同祖先。然而，与我们之前的报告相反，没有发现 LITR 的 Ig 样结构域与 LRC 编码的哺乳动物免疫调节受体的 Ig 样结构域之间的系统发育关系的支持性证据。我们还在斑马鱼基因组中发现了一个类似 LRC 的区域，但在该区域中没有发现与litr相关的基因。同样，没有lilr相关基因在斑点雀鲷中发现，这是一种代表性的基础鳍鳍鱼。最后，在象鲨基因组中发现了两个远缘 fcrls和一个 LRC 样基因，这表明含有免疫调节受体的 LRC 区域的丢失可能是射线鳍鱼所独有的。