STAT1 and head and neck squamous cell carcinoma: Furthermore, STAT1 deficiency in HNSCC models (Stat1−/− mice) resulted in increased infiltration of MDSCs (CD11b + Ly6G+) and M2 macrophages (F4/80 + CD206+), underscoring the importance of STAT1 in restraining these immunosuppressive myeloid populations [20].