RNASEL and COVID-19: PKR and OAS-RNase L are activated in SARS-CoV-2-infected lung cell line Calu-3 and A549.429 Mesenchymal stem cells in bronchoalveolar lavage samples from severe COVID-19 patients exhibit upregulated PKR compared with cells from mild patients.417 Additionally, autosomal recessive OAS-RNase L deficiencies are responsible for SARS-CoV-2-related multisystem inflammatory syndrome in children.430