Expression of PD-L1 on regulatory B cells in patients with acute myeloid leukaemia and its effect on prognosis.

Programmed death-ligand 1 (PD-L1) is involved in immunosuppression in variety of tumours. Regulatory B cells (Bregs) are critical immune regulatory cells, and it has been demonstrated that the number of regulatory B cells in patients with acute myeloid leukaemia (AML) is much higher than that in healthy donors (HDs), which is linked to a poor prognosis. This study aimed to determine whether increased expression of PD-L1, including in Bregs, is associated with a worse prognosis in individuals with AML. The proportion of Bregs, PD-L1 expression in Bregs and PD-1 expression in T cells were determined using flow cytometry using patient samples from 21 newly diagnosed AML patients at different stages of treatment and 25 HDs. We confirmed PD-L1 expression in Bregs, and PD-1 expression in CD3 + CD4 + T cells in bone marrow and peripheral blood samples from AML patients was higher than that in samples from HDs. The complete remission (CR) and progression-free survival (PFS) of Bregs with high PD-L1 expression were significantly decreased following induction chemotherapy. PD-L1 expression is indeed increased in Bregs from individuals with AML, and high PD-L1 expression is related to a poor prognosis.