Treatment with Ligands for Toll-Like Receptors 2 and 5 Induces a Mixed T-helper 1- and 2-Like Response in Chicken Splenocytes

Abstract

Toll-like receptors (TLRs) play an important role in the induction of host responses to pathogens. Interactions between TLRs and their ligands result in the production of cytokines that modulate the adaptive immune response through polarizing CD4+ T cells into either T-helper (T_H)1 or T_H2 phenotypes. In this regard, TLR2 and TLR5 ligands have been shown to induce responses in mammals that are biased toward T_H1 or T_H2 phenotypes. However, whether a similar phenomenon occurs in chickens remains to be elucidated. To this end, chicken splenocytes were stimulated with the TLR2 ligand Pam3CSK4 and the TLR5 ligand flagellin, and the relative expression of several cytokines and transcription factors was quantified at 1, 3, 8, and 18 h poststimulation. The results suggest that both TLR ligands induce a mixed T_H1- and T_H2-like response, as characterized by the upregulation of both the T_H1-associated cytokine interferon-γ and the T_H1-inducing cytokine interleukin (IL)-12, in addition to the T_H2-associated cytokine IL-4, and in the case of flagellin, IL-13 as well. Future studies may be aimed at assessing the adjuvant potential of these ligands.