CD4 and neoplasm: Adaptive immunity plays the most important role in the anti-tumor immune response.416 It has been noted that CD4+ Th1 cells, activated CD8+ T cells, and γδT cells are often involved in immune responses and have been associated with favorable prognosis in patients with lung cancer.417 In particular, CTLs are known to recognize the abnormal antigens of tumor cells, secrete granzyme and perforin to kill tumors, and express Fas-L, allowing them to bind with tumor cells to promote their apoptosis.