Uncovering a role for B cells in antitumour immunity

The function of immune cells called B cells in cancer has been controversial. Single-cell profiling has identified a previously undescribed subset of B cells that express a protein called TIM-1 and that multiply in response to melanoma tumour growth. Deletion of the gene that encodes TIM-1 in these cells unleashed an antitumour immune response. Deletion of a protein called TIM-1 from B cells reduces tumour burden in a mouse model of skin cancer.