Polymorphisms of chicken toll-like receptor 1 type 1 and type 2 in different breeds.

Toll-like receptors (TLR) mediate immune responses via recognition of pathogen-associated molecular patterns, thus playing important roles in the host defense. Polymorphisms of TLR may affect their recognition of pathogen-associated molecular patterns, leading to varied host resistance to pathogenic infections. However, little is known regarding the polymorphisms of chicken TLR (ChTLR) among breeds. In this study, we cloned ChTLR1 type 1 and type 2 genes from 9 chicken breeds (2 commercial breeds and 7 Chinese native breeds) and analyzed their sequences. We found 27 amino acid polymorphism sites in ChTLR: 14 sites in type 1 (8 sites in the extracellular domain, 5 sites in the cytoplasmic domain, and 1 site in the transmembrane domain) and 13 sites in type 2 (11 sites in the extracellular domain, 1 site in the cytoplasmic domain, and 1 site in the transmembrane domain). These results demonstrate that ChTLR1 type 1 and type 2 genes are polymorphic among chicken breeds, suggesting a varied resistance among breeds of chicken. This information provides new consideration for future poultry breeding and breed improvement.