As environments and pathogen landscapes shift, host defenses must evolve to remain effective. Due to this selection pressure, among-species comparisons of genetic sequence data often find immune genes to be among the fastest evolving genes across the genome. The full extent and nature of these immune adaptations, however, remain largely unexplored. In a recent study, we analyzed patterns of selection within distinct components of the Drosophila melanogaster immune pathway. While we found evidence of positive selection within some immune processes, immune genes were not universally characterized by signatures of strong selection. On the contrary, we even found that some immune functions show greater than expected constraint. Overall these results highlight 2 major factors that appear to play an outsize role in determining a gene's evolutionary rate: the type of pathogen the gene targets and the gene's position within the immune network. These results join a growing body of literature that highlight the complexity of immune adaptation. Rather than there being uniformly strong selection across all immune genes, a combination of pathogen-specificity and host genetic constraints appear to play key roles in determining each immune gene's individual evolutionary trajectory.

随着环境和病原体景观的变化，宿主防御必须不断发展以保持有效。由于这种选择压力，遗传序列数据的种间比较经常发现免疫基因是整个基因组中发展最快的基因之一。但是，这些免疫适应的全部范围和性质仍未得到充分探索。在最近的研究中，我们分析了果蝇果蝇不同组成部分的选择模式免疫途径。尽管我们发现在某些免疫过程中存在阳性选择的证据，但免疫基因并未普遍具有强选择的特征。相反，我们甚至发现某些免疫功能显示出超出预期的限制。总的来说，这些结果突显了两个主要因素，这些因素似乎在决定基因的进化速率中起着举足轻重的作用：该基因靶向的病原体类型和该基因在免疫网络中的位置。这些结果加入了越来越多的文献，这些文献突显了免疫适应的复杂性。病原体特异性和宿主遗传限制相结合似乎在决定每个免疫基因的个体进化轨迹中起着关键作用，而不是在所有免疫基因上都具有统一的强选择。