Polymorphisms of chicken Toll-like receptors 4, 15, and 21 in different breeds

Toll-like receptors (TLR) mediate immune responses via the recognition of pathogen-associated molecular patterns, thus playing important roles in host defense. Among the chicken (Ch) TLR family; ChTLR1, 2, 4, 15, and 21 were shown to recognize bacterial components. In our earlier study; we reported polymorphisms of TLR1, 2, and 5. In the present study, we cloned TLR4, 15, and 21 genes from different chicken breeds and analyzed their sequences. We identified 9 amino acid polymorphism sites in ChTLR4 with 8 extracellular domain sites and 1 site in the cytoplasmic domain; 15 amino acid polymorphism sites in ChTLR15 with 14 extracellular domain sites and 1 site in the cytoplasmic domain, and 7 amino acid polymorphism sites in ChTLR21 with 5 extracellular domain sites and 2 sites in the cytoplasmic domain. These results demonstrate that ChTLR genes are polymorphic among different avian breeds, suggesting a varied resistance across numerous chicken breeds. This information might help improve chicken health by breeding and vaccination.