In patients diagnosed with COVID-19, some exhaustion markers including lymphocyte-activation gene 3 (LAG3), T cell immunoglobulin and mucin domain containing protein 3 (TIM-3), programmed cell death protein 1 (PDCD1) and hepatitis A virus cellular receptor 2 (HAVCR2) have been characterized on NK cells (Figure 1C). The gene discussed is PDCD1; the disease is COVID-19.