Bacterial and viral induction of chicken thrombocyte inflammatory responses

• Chicken thrombocytes express Toll-like receptors (TLRs) that are important for anti-microbial host defense.
• Thrombocytes demonstrate differential responses when stimulated with various TLR ligands.
• TLR4 and TLR2 ligand stimulation increased IL-6 expression while TLR3 and TLR7/8 ligand increased nitric oxide production.
• Compared to MQ.NCSU macrophages, thrombocytes were able to respond much more rapidly when exposed to TLR ligands.

Thrombocytes express Toll-like receptors (TLRs) that detect bacterial or viral pathogens to signal the release of cytokines and mediators. We examined inflammatory responses when thrombocytes were exposed to four TLR ligands. Treatment of thrombocytes with TLR ligands demonstrates differential effects on gene expression of interleukin (IL)-6. Among the TLR ligands examined, lipopolysaccharide stimulation led to the most significant up-regulation of the IL-6 gene and a significant amount of active IL-6 in thrombocyte culture media. Lipoteichoic acid stimulation led to only marginal up-regulation of IL-6 gene expression. Although gene expression of inducible nitric oxide synthase (iNOS) did not increase due to different ligand exposure, a low level constitutive expression of iNOS was observed in all cases. Only thrombocytes treated with polyinosinic–polycytidylic acid and thymidine homopolymer phosphorothioate oligodeoxynucleotides induced rapid, significant production of nitric oxide. We also observed that thrombocytes are able to respond faster upon TLR ligand exposure compared to MQ.NCSU macrophages.