Bioinformatics analysis of the chicken genome revealed a pathogen recognition receptor - TLR15, whose ortholog is absent in mammals [Higgs R et al 2006]. TLR15 orthologs were also found in other avian genomes - turkey, duck and zebra finch [Boyd AC et al 2012].
Chicken tlr15 gene was mapped on chromosome 3 and encodes a protein that like other TLRs consists of a cytoplasmic Toll/IL-1 receptor (TIR) region, a transmembrane domain, and an extracellular domain with multiple leucine-rich regions (LRR) [Higgs et al 2006]. However, phylogenetic analysis revealed that TLR15 does not belong to any of the TLR groups identified to date [Temperley ND et al 2008; Boyd AC et al 2012].
TLR15 mRNA was detected in a broad range of chicken tissues: spleen, thymus, ileum, colon, bursa, bone marrow, liver and cecum [Boyd AC et al 2012; Higgs R et al 2006].
Modeling of the TLR15 TIR domain revealed the presence of a conserved BB-loop structure including a conserved proline residue, known to be required for MyD88-dependent signaling in mammalian TLR family members [deZoete MR et al 2011]. This Reactome project describes TLR15-mediated induction of MyD88 pathway in chicken, however the mechanism of TLR15-mediated responses remains unclear.