Researchers have found that CD19-positive exosomes released by B cells contained high levels of CD39 and CD73 molecules, which hydrolyse ATP released by chemotherapy-induced apoptotic tumour cells into adenosine, inhibiting the activation of CD8+ T cells during chemotherapy, thereby weakening the antitumour effects of chemotherapy [88] (Fig. 1f). Here, CD19 is linked to neoplasm.