Integrative Biology, ETH Zurich, Switzerland.
BMC Evol Biol. 2010 Dec 8;10:380. doi: 10.1186/1471-2148-10-380.
The ability of an immune system to remember pathogens improves the chance of the host to survive a second exposure to the same pathogen. This immunological memory has evolved in response to the pathogen environment of the hosts. In vertebrates, the memory of previous infection is physiologically accomplished by the development of memory T and B cells. Many questions concerning the generation and maintenance of immunological memory are still debated. Is there a limit to how many memory cells a host can generate and maintain? If there is a limit, how should new cells be incorporated into a filled memory compartment? And how many different pathogens should the immune system remember?
In this study, we examine how memory traits evolve as a response to different pathogen environments using an individual-based model. We find that even without a cost related to the maintenance of a memory pool, the positive effect of bigger memory pool sizes saturates. The optimal diversity of a limited memory pool is determined by the probability of re-infection, rather than by the prevalence of a pathogen in the environment, or the frequency of exposure.
Relating immune memory traits to the pathogen environment of the hosts, our population biological framework sheds light on the evolutionary determinants of immune memory.
免疫系统记住病原体的能力提高了宿主第二次接触同种病原体时存活的机会。这种免疫记忆是为了应对宿主的病原体环境而进化的。在脊椎动物中，记忆 T 细胞和 B 细胞的发育实现了对先前感染的记忆。许多关于免疫记忆的产生和维持的问题仍在争论中。宿主能产生和维持的记忆细胞数量是否有限制？如果有限制，新细胞应该如何融入充满的记忆区？免疫系统应该记住多少种不同的病原体？
在这项研究中，我们使用基于个体的模型来研究记忆特征如何作为对不同病原体环境的反应而进化。我们发现，即使没有与记忆池维持相关的成本，更大的记忆池大小的积极效应也会饱和。有限记忆池的最佳多样性取决于再感染的概率，而不是病原体在环境中的流行程度，也不是暴露的频率。
将免疫记忆特征与宿主的病原体环境联系起来，我们的群体生物学框架揭示了免疫记忆的进化决定因素。
