CD4 and viral infectious disease: While TH2 responses are generally considered less protective against viral infections, TH2 expansion might represent a regulatory response to limit excessive TH1/TH17-mediated inflammation, and a recent study found enrichment of the expression TH2 cytokines in long-persisting CD4 T-cell clones (57), suggesting that these cells might play a role in the long-term protection against SARS-CoV-2.