Stress, Hypoxia, and Immune Responses

Humans subjected to hostile environments are more prone and vulnerable to infections due to the complex interaction of various stressors. Besides other mechanisms known to induce immune imbalance and suppression as described in this book, this chapter focuses on the still very little known role of hypoxia-triggered immunosuppressive mechanisms in astronauts/cosmonauts e.g. during long-duration space missions. This chapter hence addresses the question of whether stress encountered by astronauts/cosmonauts might trigger neurohumoral effector mechanisms leading to tissue hypoxia thereby causing up-regulation of anti-inflammatory pathways. Such hypoxia signaling-dependent pathways might act additionally to those stimulated by neurohumoral mediators of the stress response even in the absence of hypoxia i.e. under normoxia. Altogether, hypoxic and normoxic pathways of the neurohumoral stress response may synergistically result in immunosuppression.