IFNG and COVID-19: HLA-DR expression on monocytes showed a significant inverse correlation with the three highest cytokines in COVID-19 patients: IL-6 (r = −0.36, p < 0.001), G-CSF (r = −0.22, p = 0.02) and CXCL10 (r = −0.22, p = 0.01); and also with CCL2 (r = −0.28, p = 0.001), together with a direct correlation with IFN-γ (r = 0.22, p = 0.04) (Figure 2D).