IL18 and COVID-19: The basis to study neutrophils is further supported by scRNA-seq documentation of increased expression of receptors to cytokines increased in ARDS33 and/or in COVID-19-ARDS34, such as: interleukin (IL)-IL-6, IL-8, IL-1β, IL-18, and tissue necrotic factor-alpha (TNF-α)35 (Supplementary Fig. S3G).