CXCL9 and COVID-19: Regarding chemokines, the spike-specific IgG/IgM were associated positively with C-X-C motif ligand (CXCL) 5 but negatively with C-C motif ligand (CCL) 4, CXCL9, CXCL10, and CXCL11, which were reportedly upregulated in severe COVID-19 [17].