Molecular identification and characterisation of a novel chicken leukocyte immunoglobulin-like receptor A5

1. Leukocyte immunoglobulin-like receptor A5 (LILRA5) is a key molecule that regulates the immune system. However, the <i>LILRA5</i> gene has not been characterised in avian species, including chickens. The present study aimed to identify and functionally characterise <i>LILRA5</i> identified from two genetically disparate chicken lines, <i>viz</i>., Marek’s disease (MD)-resistant (R) line 6.3 and MD-susceptible (S) line 7.2. 2. Multiple sequence alignment and phylogenetic analyses confirmed that the identity and similarity homologies of amino acids of LILRA5 in chicken lines 6.3 and 7.2 ranged between 93% and 93.7%, whereas those between chicken and mammals ranged between 20.9% and 43.7% and 21.1% to 43.9%, respectively. The newly cloned <i>LILRA5</i> from chicken lines 6.3 and 7.2 revealed high conservation and a close relationship with other known mammalian LILRA5 proteins. 3. The results indicated that LILRA5 from chicken lines 6.3 and 7.2 was associated with phosphorylation of Src kinases and protein tyrosine phosphatase non-receptor type 11 (SHP2), which play a regulatory role in immune functions. Moreover, the results demonstrated that <i>LILRA5</i> in these lines was associated with the activation of major histocompatibility complex (MHC) class I and β2-microglobulin and induced the expression of the transporter associated with antigen processing. In addition, <i>LILRA5</i> in both chicken lines activated and induced Janus kinase (JAK)–signal transducer and the activator of transcription (STAT), nuclear factor kappa B (NF-κB), phosphoinositide-3-kinase (PI3K)/protein kinase B (AKT) and the extracellular signal-regulated kinase (ERK)1/2 signalling pathways; toll-like receptors; and Th1-, Th2-, and Th17- cytokines. 4. The data suggested that LILRA5 has innate immune receptors essential for macrophage immune response and provide novel insights into the regulation of immunity and immunopathology.

1. 白细胞免疫球蛋白样受体A5（Leukocyte immunoglobulin-like receptor A5，LILRA5）是调控免疫系统的关键分子。然而，迄今尚未在包括家鸡在内的禽类物种中对<i>LILRA5</i>基因开展功能鉴定。本研究旨在从两个遗传背景迥异的鸡品系——抗马立克氏病（Marek’s disease，MD）品系6.3（R系）以及易感马立克氏病品系7.2（S系）中鉴定<i>LILRA5</i>基因，并对其进行功能表征。
2. 多序列比对与系统发育分析结果证实，6.3与7.2号鸡品系中LILRA5的氨基酸一致性与相似性同源性范围为93%~93.7%；而鸡与哺乳动物的LILRA5氨基酸一致性与相似性同源性范围分别为20.9%~43.7%与21.1%~43.9%。从上述两个鸡品系中新克隆得到的<i>LILRA5</i>基因，与已报道的其他哺乳动物LILRA5蛋白具有高度保守性且亲缘关系紧密。
3. 研究结果显示，6.3与7.2号鸡品系来源的LILRA5可与Src激酶及蛋白酪氨酸磷酸酶非受体型11（SHP2）的磷酸化过程相关联，而二者均在免疫功能中发挥调控作用。此外，结果证实上述两个鸡品系中的<i>LILRA5</i>与主要组织相容性复合体（MHC）I类分子及β2微球蛋白（β2-microglobulin）的激活相关，并可诱导抗原加工相关转运体的表达。进一步研究发现，两个鸡品系中的<i>LILRA5</i>均可激活并诱导贾纳斯激酶（JAK）-信号转导与转录激活因子（STAT）、核因子κB（NF-κB）、磷脂酰肌醇3-激酶（PI3K）/蛋白激酶B（AKT）及细胞外调节蛋白激酶（ERK）1/2信号通路，同时可调控Toll样受体以及Th1、Th2、Th17型细胞因子的表达。
4. 本研究数据表明，LILRA5作为固有免疫受体，对巨噬细胞的免疫应答至关重要，同时为免疫系统调控及免疫病理机制研究提供了全新视角。