The PD-1 mAb clone EH12.EH7 (Biolegend) used in the current study has been used previously by other investigators to detect PD-1 expression on CD8+ T cells in lymph nodes of SIV-infected rhesus macaques (62) and in esophageal carcinomas in humans (63). The gene discussed is CD8A; the disease is carcinoma of esophagus.