Reconstitution of monocyte subsets and pd‐l1 expression but not t cell pd‐1 expression in obstructive sleep apnea patients upon pap therapy

Obstructive sleep apnea (OSA) is characterized by nocturnal breathing intermissions resulting in oxidative stress and eventually, a low‐grade systemic inflammation. The study aimed to investigate the impact of positive airway pressure (PAP) therapy on the inflammatory milieu as measured by monocyte and T cell phenotypic alterations. Participants were assessed for their OSA severity before PAP therapy and about six months later, including patient‐reported outcome and therapy usage by telemetry readout. The distributions of the CD14/CD16‐characterized monocyte subsets as well as the CD4/CD8‐characterized effector T cell subsets with regard to their PD‐1 and PD‐L1 expression were analyzed by flow cytometry from blood samples. Data of 25 patients revealed a significant reconstitution of the monocyte subset distribution and a decrease in PD‐L1 expression on pan‐monocytes and CD8⁺ T cells without an association to initial AHI and overweight. The PD‐1 expression was still increased on T cell subsets, especially on CD4⁺ TH17/22 cells. We conclude that PAP therapy might have a rapid effect on the monocyte phenotype and overall PD‐ L1 expression levels. However, T cell immune alterations especially on TH17/22 cells persist longer, indicating an ongoing disturbance of the adaptive immune system.