Characterization of responses elicited by Toll-like receptor agonists in cells of the bursa of Fabricius in chickens.

Toll-like receptors (TLRs) are an evolutionarily conserved group of pattern recognition receptors that play an important role in mediating host-responses to pathogens. Several TLRs have been identified in chickens and their expression has been detected in many immune cell subsets including in B cells. However, the mechanisms through which TLRs modulate B cell responses have not been well characterized in chickens. The aim of the present study was to elucidate the responses mounted by cells of the bursa of Fabricius to treatment with the TLR 3, 4 and 21 ligands, poly I:C, lipopolysaccharide (LPS) and CpG oligodeoxynucleotides (ODN), respectively. The relative expression of several immune system genes was quantified at 1, 3, 8 and 18 h post-treatment. The results show that all three ligands induced the up-regulation of interferon (IFN)-γ and interleukin (IL)-10 transcripts and promoted the up-regulation of transcripts associated with antigen presentation, namely CD80 and major histocompatibility complex (MHC) class II. Furthermore, the results indicated that LPS and poly I:C induced the greatest IFN-γ and IL-10 responses, respectively, while CpG ODN was the most efficacious inducer of CD80 and MHC-II expression. Future studies may be aimed at elucidating the mechanisms of TLR-mediated activation of chicken B cells. These mechanisms may be then exploited for the development of adjuvants with enhanced ability to stimulate B cell responses.