Characterization of Chicken Tumor Necrosis Factor-α, a Long Missed Cytokine in Birds

Abstract

Tumor necrosis factor-α (TNF-α) is a pleiotropic cytokine playing critical roles in host defense and acute and chronic inflammation. It has been described in fish, amphibians, and mammals but was considered to be absent in the avian genomes. Here, we report on the identification and functional characterization of the avian ortholog. The chicken TNF-α (chTNF-α) is encoded by a highly GC-rich gene, whose product shares with its mammalian counterpart 45% homology in the extracellular part displaying the characteristic TNF homology domain. Orthologs of chTNF-α were identified in the genomes of 12 additional avian species including Palaeognathae and Neognathae, and the synteny of the closely adjacent loci with mammalian TNF-α orthologs was demonstrated in the crow (Corvus cornix) genome. In addition to chTNF-α, we obtained full sequences for homologs of TNF-α receptors 1 and 2 (TNFR1, TNFR2). chTNF-α mRNA is strongly induced by lipopolysaccharide (LPS) stimulation of monocyte derived, splenic and bone marrow macrophages, and significantly upregulated in splenic tissue in response to i.v. LPS treatment. Activation of T-lymphocytes by TCR crosslinking induces chTNF-α expression in CD4+ but not in CD8+ cells. To gain insights into its biological activity, we generated recombinant chTNF-α in eukaryotic and prokaryotic expression systems. Both, the full-length cytokine and the extracellular domain rapidly induced an NFκB-luciferase reporter in stably transfected CEC-32 reporter cells. Collectively, these data provide strong evidence for the existence of a fully functional TNF-α/TNF-α receptor system in birds thus filling a gap in our understanding of the evolution of cytokine systems.

The Impact of Probiotics and Egg Yolk IgY on Behavior and Blood Parameters in a Broiler Immune Stress Model

“…Elevation of the H/L ratio, heterophil differential counts, and eosinophil differential counts in the birds challenged with LPS is considered to be due to the binding of LPS to toll-like receptor 4 on immune cells. This binding promotes proinflammatory cytokines production, including TNF-α, TNF-γ, and IL-6, followed by induction of heterophil proliferation in the innate immune response (54). The ability of IgY to decrease the acute elevation of the immune cell count might help to avoid the undesirable effects of inflammation while maintaining a passive immunization.…”

Pathogenicity and Immune Responses of Aspergillus fumigatus Infection in Chickens

“…Primers ( Table 1) required in the study were designed using the Primer 3 online software (http://bioinfo.ut. ee/primer3-0.4.0/) based on the published GenBank sequence or refer to other study (32). Quantitative real-time PCR (qPCR) was prepared in 20 µL according to the operation instruction (Vazyme, Nanjing, China) and performed using Roche LightCycler 96 (Roche, Basel, Switzerland).…”

Neurons and astrocytes of the chicken hypothalamus directly respond to lipopolysaccharide and chicken interleukin-6

“…The neuron also responded to buffer containing a high concentration of KCl (50 mM) with a pronounced increase of [Ca 2+ ] i , whereas the KCl response is missing in the astrocyte Garami et al 2019). Interestingly, of these proinflammatory cytokines TNF-α was supposed to be absent in the avian genome (Staeheli et al 2001) until it was recently identified and characterized in chicken (Rohde et al 2018). The lack of pronounced hypothermia in birds under these conditions might be due to the lack of a significant contribution of TNF-α to the thermal response to LPS in birds.…”

“…The lack of pronounced hypothermia in birds under these conditions might be due to the lack of a significant contribution of TNF-α to the thermal response to LPS in birds. Whether there is a significant contribution of this recently discovered avian cytokine (Rohde et al 2018) in LPS fever in birds at all will have to be determined. For other cytokines with pyrogenic properties, i.e., IL-1β and IL-6, there is more evidence for a significant role in fever in birds (Marais et al 2011;Gray et al 2013).…”