Schwensow N, Fietz J, Dausmann K H, Sommer S
Department of Animal Ecology and Conservation, University of Hamburg, Hamburg, Germany.
Heredity (Edinb). 2007 Sep;99(3):265-77. doi: 10.1038/sj.hdy.6800993. Epub 2007 May 23.
Current discussions in evolutionary ecology and conservation genetics focus on the relative importance of using selective neutral markers or markers of coding genes to identify adaptive and evolutionary relevant processes. Genetic diversity might be particularly important in immune genes (e.g., in genes of the major histocompatibility complex, MHC), which are influencing pathogen and parasite resistance. We investigated the effects of neutral versus adaptive genetic variation in parasite resistance in a natural population of fat-tailed dwarf lemurs (Cheirogaleus medius). No association between neutral overall individual genetic diversity and parasite load could be detected. In 149 individuals, we identified 50 MHC class II alleles of the functionally important duplicated DRB locus. The investigation of the functional importance of immune gene (MHC) diversity and parasite selection in natural populations is often problematic due to extensive polymorphism in the MHC genes and restrictions in available sample sizes. Here, for the first time we applied an approach that has been developed in human medical studies. Eleven MHC class II supertypes were identified based on shared antigen-binding similarities. The number of individual MHC supertypes had no influence on the nematode burden. However, we found evidence for a specific MHC supertype (supertype 1) that was linked to infected individuals, a higher number of different nematode infections and high intensity of infection per individual. Moreover, one rare MHC supertype (supertype 7) was revealed to be advantageous with respect to parasite burden. Thus, our results add evidence to the small body of studies that show significant associations between specific MHC constitutions and naturally occurring parasites in the complexity of natural populations.
当前进化生态学和保护遗传学的讨论聚焦于使用选择性中性标记或编码基因标记来识别适应性和进化相关过程的相对重要性。遗传多样性在免疫基因（例如主要组织相容性复合体，MHC的基因）中可能尤为重要，这些基因会影响对病原体和寄生虫的抗性。我们研究了肥尾侏儒狐猴（Cheirogaleus medius）自然种群中中性与适应性遗传变异对寄生虫抗性的影响。未检测到中性的总体个体遗传多样性与寄生虫负荷之间的关联。在149只个体中，我们鉴定出了功能重要的重复DRB位点的50个MHC II类等位基因。由于MHC基因的广泛多态性和可用样本量的限制，在自然种群中研究免疫基因（MHC）多样性和寄生虫选择的功能重要性往往存在问题。在此，我们首次应用了一种在人类医学研究中开发的方法。基于共享的抗原结合相似性鉴定出了11种MHC II类超型。个体MHC超型的数量对线虫负荷没有影响。然而，我们发现有证据表明一种特定的MHC超型（超型1）与受感染个体、个体中更多不同的线虫感染以及高感染强度有关。此外，还发现一种罕见的MHC超型（超型7）在寄生虫负荷方面具有优势。因此，我们的结果为少量研究增添了证据，这些研究表明在自然种群的复杂性中，特定的MHC组成与自然存在的寄生虫之间存在显著关联。
