PD-L1 + regulatory B cells act as a T cell suppressor in a PD-L1-dependent manner in melanoma patients with bone metastasis.

•Level of PD-L1 by circulating B cells was positively associated with tumor stage.•PD-L1+ B cells exhibited a naive B cell-like phenotype.•Stage III and stage IV melanoma patient naive B cells suppressed T cell response.•The suppression was in a PD-L1-dependent manner.•The level of PD-L1+ B cells was higher in bone metastases than in the primary tumors.