CD4 and head and neck squamous cell carcinoma: IL-10+ Bregs and their positive correlation with Tregs [23], suppression of CD4+ and CD8+T cells anti-tumour responses, and their induction of a tolerant TME have now been described in numerous solid and haematological cancers including liver, cervical, ovarian, gastric, and breast cancers, head and neck squamous cell carcinoma (HNSCC) [23–26, 29, 35], acute myeloid leukaemia, and non-Hodgkin lymphoma [8, 30, 71–73].