Fig. 1: Schematic summary of the immune system activation and response to a viral infection.
From: Obesity, the most common comorbidity in SARS-CoV-2: is leptin the link?
Virion particles are illustrated by open pentagons. The three distinct types of IFNs include: type I IFNs (IFN-α and IFN-β), type II IFNs (IFN-γ), and type III IFNs (IFN-λ), All IFN types bind to distinct receptors but activate similar signaling pathways and transcriptional responses. The type I, type II, and type III IFN receptors are heterodimers composed of IFNAR1 and IFNAR2 subunits, IFNGR1 and IFNGR2 subunits, and IFNLR1 and IL10Rβ subunits, respectively. Viral-encoded products antagonize the IFN-signaling pathways and the biochemical activity of IFN-induced cellular proteins to thwart host antiviral defense. In activated lymphocytes, lipid oxidation is downregulated and glycolysis increases in the presence of oxygen, together with glutamine oxidation in order to produce the biosynthetic precursors required for rapid cell growth and proliferation. Leptin signals via the Jak/STAT and Akt pathways among others to mediate immune cell number and function. Leptin dysregulation in obesity has detrimental effects during an infection. LepR: leptin receptor.
