CD4 and neoplasm: Much research has shown that patients’ responses to immunotherapy are dependent on the level of tumor immune cell infiltration, for example, CD4+ T cells, CD8+ T cells, and natural killer T (NKT) cells contribute to the immunotherapeutic efficacy of tumors [44–48], whereas myeloid-derived suppressor cells (MDSCs) inhibit the antitumor effects of these immune cells and promote tumor progression [49].