These observations, coupled with reports of CTLA-4 expression in MDSCs and M2 macrophages in HNSCC tumors (69), underscore the importance of investigating the physiology of CTLA-4 within the monocyte lineage, particularly its utility in type I and type II T-cell responses as well as in T-cell-independent responses. This evidence concerns the gene CTLA4 and head and neck squamous cell carcinoma.