-The exposure of chicken peripheral blood mononuclear cells (PBMCs) to pathogen can induce a rapid change in both proinflammatory and anti-inflammatory cytokine gene expression. Chicken PBMCs were infected with avian pathogenic Escherichia coli (APEC) and the isogenic fimH mutants of APEC, PBMCs immune response was determined by semi-quantitative RT-PCR. The results demonstrated that PBMCs were expressed TLR1/6/10, TLR3, TLR4, TLR5 and TLR7. APEC and non pathogenic E. coli strains were significantly (P < 0.05) increased the expression of IL-1β, IL-8, IL-18 and TGF-β4 cytokines compared to the isogenic fimH mutants. In addition, the opsonized avian pathogenic E. coli strains were significantly (P < 0.05) increased the expression of cytokines compared to the non-opsonized strains, whereas the opsonized avian non-pathogenic E. coli strain was significantly (P < 0.05) decreased the expression of cytokines compared to the non-opsonized strain. PBMCs are important in APEC infection, the increase in cytokines expression may play important role in the regulation of immune response.