CD4 and neoplasm: According to the simple being test, current biomarkers are mainly including tumor tissue biomarkers [e.g. PD-L1 expression (11, 12), tumor mutation burden (TMB) (13), MHC molecule expression (14, 15)], circulating immune cells biomarkers [e.g. CD4+T cells (16, 17), myeloid-derived suppressive cells (MDSCs) (18)] and soluble systemic immune/inflammatory biomarkers [e.g. lactate dehydrogenase (LDH) (19, 20), cytokines (21, 22)].