B Cells and Melanoma Pathogenesis.

Melanoma is one of the deadliest cancers. In this issue, Kobayashi et al. (2019) demonstrate a novel role for tumor-infiltrating innate-like B1a B cells in promoting melanoma growth. IL-10+ (B1a) regulatory B cells accumulate selectively in melanomas, and enhance tumor growth through suppression of cytokine production by tumor-infiltrating CD8+ T cells and potentially additional IL-10-dependent mechanisms.