CXCL8 and COVID-19: CXCL8 is a key cytokine in COVID-19 pathogenesis, associated with adverse clinical outcomes and disease severity.23,24 Given that CXCL8 was found to be upregulated across the SARS-CoV-2 ancestral strain and variants (Figure 3A), interleukin 8 (IL-8) levels were measured in the supernatant from SARS-CoV-2-exposed MKs.