Objective To investigate the expression of programmed death receptor ligand 1 (PD-L1) in circulating B cells of patients with type 1 diabetes mellitus (T1DM).

Methods Peripheral blood samples were collected from healthy controls (n=25) and T1DM patients (n=25). The expression of PD-L1 on B cells and their surfaces was detected by flow cytometry.

Results There was no significant difference in the frequency of B cell subsets between the T1DM patients and healthy controls (P>0.05). Compared with healthy controls, the expression of PD-L1 on CD19⁺ cells, CD19⁺CD27⁺ cells and CD19⁺CD27⁺ cells in the T1DM patients was significantly decreased (P < 0.05). There was no significant difference in the expression of PD-L1 in B10 cells, marginal zone B cells (MZB) and follicular B cells (FoB) between healthy controls and T1DM patients (P>0.05). The expression of PD-L1 on transitional 2-marginal zone precursor B cells (T2-MZP) cells in the T1DM patients was lower than that in the healthy controls (P < 0.05).

Conclusion The PD-L1 may play a protective role in the pathogenesis of T1DM. B cells with high expression of PD-L1 may provide a new strategy for the treatment of patients with autoimmune diabetes.