Association between programmed death-1 pathway and major depression.

Objectives: Major depression (MD) may be associated with inflammation and immunity. PD-1 (programmed death-1), PD-L1 (programmed death-ligand 1) and PD-L2 (programmed death-ligand 2) are among the inhibitory immune mediators on the PD-1 pathway. However, previous data regarding the association between MD and PD-1 pathway were still scarce; therefore, we investigated the association of PD-1 pathway with MD.

Methods: During a period of 2 years, patients with MD and healthy controls were recruited from a medical centre in this study. The diagnosis of MD was established according to the DSM-5 criteria. The severity of MD was assessed with 17-item Hamilton Depression Rating Scale. PD-1, PD-L1 and PD-L2 were detected in peripheral blood from MD patients after 4 weeks of treatment with antidepressant drugs.

Results: A total of 54 patients with MD and 38 healthy controls were recruited. According to the analyses, there is a significantly higher PD-L2 level in MD than in healthy controls and lower PD-1 level after age and BMI adjustment. Besides, moderately positive correlation between HAM-D scores and PD-L2 level was found.

Conclusions: It was found that PD-1 pathway might play an important role in MD. We need a large sample to prove these results in the future.