ICOS and melanoma: TGF-β+ B cells have senescent properties and may support the differentiation and maintenance of Tregs in melanoma lesions through expression of Galectin-9, while TNF-α+ B cells may engage in extensive crosstalk with Tregs, including via ICOS, TNF-α, LT-α, and MIF signaling, which are likely to support the suppressive activity of Tregs in the melanoma TME.