The evolution of resistance through costly acquired immunity

Abstract

We examine the evolutionary dynamics of resistance to parasites through acquired immunity. Resistance can be achieved through the innate mechanisms of avoidance of infection and reduced pathogenicity once infected, through recovery from infection and through remaining immune to infection: acquired immunity. We assume that each of these mechanisms is costly to the host and find that the evolutionary dynamics of innate immunity in hosts that also have acquired immunity are quantitatively the same as in hosts that possess only innate immunity. However, compared with resistance through avoidance or recovery, there is less likely to be polymorphism in the length of acquired immunity within populations. Long-lived organisms that can recover at intermediate rates faced with fast-transmitting pathogens that cause intermediate pathogenicity (mortality of infected individuals) are most likely to evolve long-lived acquired immunity. Our work emphasizes that because whether or not acquired immunity is beneficial depends on the characteristics of the disease, organisms may be selected to only develop acquired immunity to some of the diseases that they encounter.

Evolution of transgenerational immunity in invertebrates

“…should be maximized in species with high or intermediate lifespan [4,[35][36][37][38]. Simply put, short-lived hosts are unlikely to encounter the same pathogen twice and should therefore not invest in memory.…”

Host resistance and coevolution in spatially structured populations

“…It is important to apply the results to more general host-parasite systems by extending the model to incorporate processes such as recovery, infected reproduction and immunity. Furthermore, modification to the analysis should also study the evolution of alternate modes of defence, such as tolerance [15,16] or acquired immunity [44] in a spatial setting. In particular, tolerance is likely to have very different evolutionary dynamics when compared with resistance, as it will increase local prevalence which would select against defence in a local population.…”

Seasonality, cohort-dependence and the development of immunity in a natural host–nematode system

“…Vertebrates often mount a significant immune response to helminth parasites, and this is found to be an important determinant of the epidemiology in human and animal hosts (Anderson & May 1991;Grenfell et al 1995a;Lloyd 1995). Moreover, immune-mediated resistance is thought to have shaped the coevolutionary history of host-parasite relationships in natural populations (Dwyer et al 1990;Boots & Bowers 2004). However, very little is known about the importance of immunity as a modulator of infection during the host's lifetime in natural populations.…”