NOS2 and lung cancer: Myeloid‐derived suppressor cells (MDSCs) are the currently identified immune cells that inhibit B‐cell proliferation in the TME.[41] In a mouse model of lung cancer, MDSCs inhibit B‐cell proliferation through inducible nitric oxide synthase (iNOS) and arginase 1 (ARG1).[41] Several previous studies have also demonstrated a negative regulatory effect of MDSCs on B‐cell proliferation.[41, 42, 43] As an important immunosuppressive molecule, TGF‐β has also been suggested to potentially impair B‐cell proliferation.[44, 45]