CD4 and neoplasm: In HPV-positive HNSCC, an increase in the infiltration of immunocompetent cells, i.e., T cells, including CD3+, CD4+, CD8+ IFN-γ cytotoxic T cells (CTLs), CD19+/CD20+ B cells, CD56dim/CD16bright activated NK cells, tumour infiltrating antigen presenting cells/dendritic cells (APCs/DCs) and myeloid and plasmacytoid dendritic cells (MDCs), and a decrease of CD4+CD25+Foxp3+ regulatory T cells in TILs is observed, which enhances the stimulation of cellular immunity to tumour antigens [298,304,315].