Cellular Immune Dysfunction in Obstructive Sleep Apnea

Abstract

Obstructive sleep apnea (OSA) is the most common sleep-related breathing disorder. Repetitive pauses in breathing during sleep cause a brief but recurrent decrease in oxygen saturation in organs and tissues (chronic intermittent tissue hypoxia). Many studies have proven a pro-inflammatory status in OSA patients. However, few reports are available on the effects of OSA on the cellular immune system, mostly focusing on single immune cell types and their subtypes. The aim of this Mini-Review is to summarize these reports, as OSA is associated with a high prevalence and comorbidities such as atherosclerosis, which are known to involve the cellular immune system.

Keywords: B cells; T cells; cellular immune system; dendritic cells; interleukins; monocytes; natural killer cells; obstructive sleep apnea.

Figure 1

Versatile effects of obstructive sleep apnea and chronic intermittent hypoxia on the cellular immune system. Arrow up: Increase in cell population; Arrow down: Decrease in cell population; Arrow to right: No change in cell population (in OSA patients compared to respective control group). Both increased and decreased levels of reactive oxygen species (ROS) in neutrophil granulocytes have been reported (37, 38). Similarly, there are both observations on NK, NKT, and B cells describing an increase and a decrease in the respective cell population (3, 31, 32, 36, 44). CD4⁺ effector T cells have been detected at increased levels in OSA patients (21). CD8⁺ T cells were found in both increased and decreased concentrations compared with the corresponding control group (–33). Both T_H17 cells and γδ T cells were detected in increased concentrations in the blood of OSA patients and in cell culture experiments, respectively (–30). Regulatory T cells have been described in reduced numbers in OSA patients (28) or at unaltered population levels (31). Studies describe that chronic intermittent hypoxia both has no effect on the population of dendritic cells (31) and leads to a decrease of these (34). Within the monocyte subpopulations, a decrease in classical monocytes and an increase in CD16⁺ subtypes (intermediate, non-classical) have been documented in OSA patients (21).