CD4 and neoplasm: However, in the past decades, the major research focus regarding tumor-infiltrating immune cells has been the tumor-infiltrating lymphocytes, including CD4+ T cells, CD8+ T cells, and regulatory T cells, while the role of antigen-presenting cells, such as myeloid dendritic cells (mDC) and plasmacytoid dendritic cells (pDC), has not been widely explored 9-11.