Link to a study on rattlesnakes: When less means more: dehydration improves innate immunity in rattlesnakes.
The results from our dilution of plasma samples from dehydrated snakes indicate that elevated immune scores associated with dehydration were not simply the result of dehydration causing increased concentration of immune factors within the plasma. This suggests that plasma proteins associated with innate immunity are upregulated (in terms of number or activity) during periods of dehydration. While innate immune performance gradually increased as animals gradually dehydrated over 16 weeks, it rapidly decreased after animals were given access to water and subsequently rehydrated quickly. This suggests that plasma proteins responsible for our findings rapidly disassociate or become ineffective.
Innate immune function provides a rapid, broadly reactive response using general effector mechanisms that are often sufficient to control infections. Innate immunity, however, also has an integral role in informing the adaptive immune system to make an overwhelming, tailored response.
Given the interconnected relationship between the innate and adaptive branches, it is reasonable to suspect that adaptive responses will be enhanced as well, and future research should explore this area.
In addition to understanding the proximate mechanisms behind our findings, it is also appropriate to consider ultimate mechanisms that might explain the perhaps initially counter-intuitive positive relationship between dehydration and innate immunity. Dehydration creates a homeostatic imbalance, which may leave the animal vulnerable to disease. Accordingly, it would be advantageous to increase innate defenses (such as complement) to defend the body from such threats. The classic dogma of immune function is that it exists to ward off harmful pathogens; however, recent evidence suggests that immunocompetence may also play a major role in maintaining physiological (Kotas and Medzhitov, 2015; Marques et al., 2016) and neurological (D'Acquisto, 2016) homeostasis.