The effects of chronic fatigue and chronic stress on alterations in immune cell responses to acute psychosocial stress

Fatigue is a common and debilitating symptom of a broad spectrum of diseases. Previous research has shown that individuals suffering from chronic forms of fatigue experience significantly more stress compared to healthy individuals, suggesting that stress is a potential pathophysiological factor in the onset and maintenance of chronic fatigue. Individually, chronic experiences of fatigue and stress have been associated with disruptions in adaptive immunity. However, how chronic fatigue and chronic stress together affect immune regulation is not fully understood. Here, we investigated the unique and combined contribution of chronic fatigue and chronic stress on immune cell redistribution in response to, and recovery from, acute psychosocial stress. Eighty women with high or low levels of chronic fatigue and varying levels of chronic stress were exposed to a psychosocial laboratory stressor. Blood samples were collected 10 min before and then at 10, 40, and 100 min after the end of stress. The main lymphocyte subpopulations (CD3+, CD3 + CD4+, CD3 + CD8+, CD16 + CD56+, and CD19 + cells) were enumerated via flow cytometry. Acute stress resulted in an increase in CD8 + and CD16+/CD56 + cells, a decline in CD4 + cells, and no effects on CD19 + B lymphocytes. Importantly, the magnitude of immune cell redistribution during stress reactivity (CD3+, CD4+, CD16+/CD56 + ) and recovery (CD3 + ) was contingent on fatigue and chronic stress levels of individuals. Notably, in contrast to low-fatigued individuals, who showed steeper changes in cell populations, increasing levels of chronic stress did not impact immune cell migration responses in high-fatigued individuals. Our findings demonstrate the compounded blunting effects of fatigue and chronic stress on adaptive immune functioning, highlighting a potential pathway for vulnerability and detrimental effects on long-term health.