Co-stimulation with TLR3 and TLR21 ligands synergistically up-regulates Th1-cytokine IFN-γ and regulatory cytokine IL-10 expression in chicken monocytes

► Chicken TLR3 and TLR21 recognize poly I:C and CpG-ODN. ► Poly I:C and CpG-ODN induce a differential expression of IFN-α, IFN-β, IFN-γ, IL-4, IL-10, and IL-12 in chicken monocytes. ► Co-stimulation with poly I:C and CpG-ODN synergistically up-regulates the expression of IFN-γ and IL-10. ► CpG-ODN and the synergy between poly I:C and CpG-ODN promote Th1-biased immune response.