The Immuno-Oxidative Ecology

Immune function plays a fundamental role in the maintenance of organismal homeostasis. It protects the organism against parasites, pathogens, toxic substances, and cancerous cells. To this end, immune function relies on a complex system, involving molecules, cells, and tissues. However, immune responses against harmful agents carry different types of costs for the host that can manifest themselves in diverse ways, such as increased metabolic rate or trade-offs with other life processes (e.g. reduced growth or fertility). The emergence of these costs would explain why we observe a wide individual variation in immunological function. But how are these costs incurred? A pillar of the immuno-oxidative ecology is that oxidative stress is a major physiological cost of immune function that mediates the trade-off between the expression of life-history traits and the need to mount an immune response. In this chapter, I have reviewed (i) the main molecular and cellular mechanisms through which immune function generates oxidative stress, (ii) the studies that tested the effects of antigen injection and parasite exposure on oxidative damage and antioxidant levels in a wide range of vertebrates, and (iii) the ways by which pathogens respond to or evade the pro-oxidant attack generated by the host to kill them.