FOXP3 and neoplasm: Enriched circulating and tumor-infiltrating TGFβ+ B cells in advanced melanoma favor FoxP3+ Treg (Forkhead box P3+ regulatory T cell) expansion in a TGFβ-dependent manner,7 and IgG4+CD49b+CD73+ Bregs (regulatory B cells) produce pro-angiogenic and inflammatory mediators (eg, vascular endothelial growth factor).9