Antiviral signalling is an important aspect of the immune response that defends against viral infections. It involves mechanisms to detect viral replication, activate immune defences, and destroy virus-infected cells, relying on specialized sensors, signalling pathways, and effector molecules. Host Pattern Recognition Receptors (PRRs) recognize specific patterns associated with viral infections, known as pathogen-associated molecular patterns (PAMPs). Virus RNA-recognizing RIG-I-like receptors (RLRs), and cytosolic viral DNA sensors (cGAS-STING) are important PRRs involved in anti-viral signalling, along with Toll-like receptors (TLRs). RLRs, including RIG-I (Retinoic Acid-Inducible Gene I) and MDA5 (Melanoma Differentiation-Associated Protein 5), recognize viral RNA molecules, with RIG-I recognizing short double-stranded RNA molecules and MDA5 recognizing long double-stranded viral RNA. Both activate downstream signalling pathways upon binding to viral RNA, undergoing conformational changes and thereby exposing Caspase Activation and Recruitment Domains (CARDs). Such binding-competent CARD domains then interact with the CARD domain of the adaptor protein MAVS (Mitochondrial Antiviral signalling protein), forming the MAVS signalosome. This complex subsequently recruits the protein kinases TBK1 (TANK-binding kinase 1) and IKKε (IκB kinase ε) which in turn phosphorylate the transcription factors IRF3 (Interferon Regulatory Factor 3) and IRF7. IRF3/7 then enter the nucleus and induce the transcription of type I interferons (IFN-α and IFN-β) and other pro-inflammatory cytokines. Type I interferons initiate the Janus kinase (JAK)-signal transducer and activator of transcription (STAT) signalling pathway in neighbouring cells, leading to the expression of many interferon-stimulated genes (ISGs) mediating antiviral activities. Type I interferons also enhance NK cell activity, leading to the destruction of virus-infected cells. For DNA viruses, the cGAS-STING pathway is a critical antiviral defence mechanism. The activation of this pathway also leads to the production of type I interferons (IFNs) and other pro-inflammatory cytokines. The cyclic GMP-AMP synthase (cGAS) protein is a cytosolic DNA sensor that recognizes viral double-stranded DNA (dsDNA). Upon binding, cGAS undergoes a conformational change, allowing it to synthesize the cyclic dinucleotide second messenger cyclic GMP-AMP (cGAMP). cGAMP then binds to the stimulator of interferon genes (STING) protein, inducing a conformational change leading to its translocation from the ER to the Golgi apparatus. STING then recruits and activates the TBK1 (TANK-binding kinase 1) kinase, which phosphorylates IRF3 (Interferon Regulatory Factor 3) leading to the expression of type I interferons. Anti-viral signalling can also induce apoptosis in infected cells, preventing the spread of the virus. ISGs encode death ligands, caspases, and pro-apoptotic proteins such as TRAIL (TNF-related apoptosis-inducing ligand). When death ligands bind to their receptors, death receptor signalling pathways are activated, inducing the formation of death-inducing signalling complexes (DISCs). DISCs subsequently activate caspase-8, which then activates caspase-3 and caspase-7 leading to apoptosis. Finally, viruses have also evolved multiple strategies aiming at evading the host's anti-viral signalling pathways and immune responses. For example, some viruses produce proteins that inhibit the activation of IRF3 and IRF7, critical for type I interferon (IFN) production. Influenza A and Herpes Simplex viruses for example encode the NS1 protein and ICP0 proteins, respectively, which interfere with IRF3 and IRF7 function. We provide a large product catalogue of research reagents for studying antiviral signaling, including CD4 antibodies, PD-L1 antibodies, HLA G antibodies, Macrophage Inflammatory Protein 1 beta ELISA Kits, and RANTES ELISA Kits. Explore our full antiviral signaling product range below and discover more, for less.