In COVID-19 patients, histopathological evidence of a cellular inflammatory response in the brain (i.e., parenchymal infiltration of CD8+ T lymphocytes and of fewer CD4+ T cells) is at a higher level than in patients dying of severe respiratory failure, but it is at a lower level in COVID-19 patients compared to patients with long-term multiple sclerosis [98]. The gene discussed is CD4; the disease is COVID-19.