1. Leukocyte immunoglobulin-like receptor A5 (LILRA5) is a key molecule that regulates the immune system. However, the LILRA5 gene has not been characterised in avian species, including chickens. The present study aimed to identify and functionally characterise LILRA5 identified from two genetically disparate chicken lines, viz., 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 LILRA5 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 LILRA5 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, LILRA5 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.
Keywords: LILRA5; Chickens; MHC class I; cytokines; signalling pathway.