Characterization of responses initiated by different Toll-like receptor 2 ligands in chicken spleen cells.

Toll-like receptors (TLRs) are pattern recognition receptors that mediate host responses to pathogens by promoting cellular activation and the production of cytokines. Ligands for TLRs are conserved structural motifs of pathogens termed pathogen-associated molecular patterns. In the case of TLR2, these ligands include peptidoglycan, lipomannan and lipopeptides. In mammals, it has been shown that different TLR2 ligands induce distinct cytokine responses. However, whether a similar phenomenon occurs in chickens remains to be determined. To this end, chicken splenocytes were stimulated with three different TLR2 ligands: Pam3CSK4, FSL-1 and lipomannan, and the relative gene expression of several cytokines was quantified at 2, 6 and 18h post-stimulation. The results suggest that Pam3 and FSL-1 modulate the kinetics of the pro-inflammatory cytokine response differently, as Pam3 induced a robust interleukin (IL)-1β response, while FSL-1 induced an early and prolonged up-regulation of IL-8. Furthermore, it appears that all three TLR2 ligands induce a mixed T-helper (TH) 1 and 2-like response, as characterized by the up-regulation of IFN-γ, IL-12, IL-4 and IL-13. In conclusion, we have demonstrated that different TLR2 ligands may induce different cytokine responses in chicken splenocytes. Future studies may be aimed at examining the immunomodulating effects of these ligands in vivo.