OAS1 (2'-5'-oligoadenylate synthetase 1) is a cytosolic double-stranded RNA sensor that functions as a key component of the innate antiviral immune response 1. Upon binding dsRNA, OAS1 catalyzes the synthesis of 2'-5'-oligoadenylates (2-5A), which activate ribonuclease L (RNase L) to degrade single-stranded RNA and restrict viral replication 1. The protein shares structural similarity with cGAS, containing a unique zinc thumb for DNA recognition, though OAS1 specifically responds to dsRNA stimuli 2. OAS1 expression is induced by type I interferons and plays regulatory roles in immune cell function, particularly in monocytes and macrophages 34. Disease relevance includes autosomal recessive OAS1 deficiency causing multisystem inflammatory syndrome in children (MIS-C) following COVID-19, where deficient cells produce excessive inflammatory cytokines upon SARS-CoV-2 stimulation 1. Conversely, gain-of-function OAS1 variants cause autoinflammatory immunodeficiency with recurrent fever, dermatitis, and pulmonary alveolar proteinosis through dsRNA-independent activation leading to inappropriate RNase L-mediated cell dysfunction 3. OAS1 also correlates with metabolic pathways and has been identified as a biomarker in systemic lupus erythematosus, highlighting its broader role in immune-metabolic interactions 45.