TNF and COVID-19: In contrast to high interferon I levels in the lungs of COVID-19 patients with severe disease [131], Hadjadj et al. found that peripheral blood immune cells in patients with severe or critical COVID-19 disease had diminished type I interferon response (absent IFN-β and low IFN-α), but enhanced proinflammatory cytokines (IL-6 and TNF-α production in the blood) [140].