Immune checkpoint inhibition demonstrated breakthrough therapeutic efficacy in cancer. Nevertheless, there is urgent need for deciphering the mode of action of checkpoint inhibition, since the majority of patients does not benefit from these therapies. Although B cells play a major part in activation of a tumor-directed immune response, their role in checkpoint therapies has largely been neglected. In this project, we aim to study the functional impact of B cells on the efficacy of checkpoint inhibition in pancreatic and gastric cancer. Elucidation of B cell specific mechanisms in the setting of checkpoint therapy could identify new therapeutic options and is of direct importance for translational analyses of ongoing clinical studies.