Signaling Pathways Downstream of Pattern-Recognition Receptors and Their Cross Talk

Pattern-recognition receptors (PRRs) initiate innate immunity through pathogen recognition. Serum PRRs opsonize pathogens for enhanced phagocytic clearance. Toll-like receptors (TLRs) initiate common NF-kappaB/AP-1 and distinct IRF3/7 pathways to coordinate innate immunity and to initiate adaptive immunity against diverse pathogens. Cytoplasmic caspase-recruiting domain (CARD) helicases, such as RIG-I/MDA5, mediate antiviral immunity by inducing the production of type I interferons via the adaptor IPS-1, whereas nucleotide-binding oligomerization domain (NOD)-like receptors mediate mainly antibacterial immunity by activating NF-kappaB or inflammasomes. Dectin-1 is important for antifungal immunity, promoting…