CD28 and gastric cancer: Marked increase in tumor‐infiltrating proliferative effector regulatory T (eTreg) cells was observed in tissue samples of gastric cancer patients,43 and a significant increase in CD4+CD25+CD127loFoxP3+ Treg cells38 or CD28− CD4+ highly differentiated T‐cells (THD)39 was independently reported from peripheral blood analysis of NSCLC patients who experienced HPD post‐immunotherapy.