Departamento de Genética, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, São Paulo, Brazil.
Departamento de Genética, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, São Paulo, Brazil.
Exp Gerontol. 2019 May;119:174-183. doi: 10.1016/j.exger.2019.02.005. Epub 2019 Feb 8.
Young honey bee workers (0 to 2-3 weeks old) perform tasks inside the colony, including brood care (nursing), whereas older workers undergo foraging tasks during the next 3-4 weeks, when an intrinsic senescence program culminates in worker death. We hypothesized that foragers are less able to react to immune system stimulation than nurse bees and that this difference is due to an inefficient immune response in foragers. To test this hypothesis, we used an experimental design that allowed us to uncouple chronological age and behavior status (nursing/foraging). Worker bees from a normal age demography colony (where workers naturally transit from nursing to foraging tasks as they age) and of a single-cohort colony setup (composed of same-aged workers performing nursing or foraging tasks) were tested for survival and capability of activation of the immune system after bacterial injection. Expression of an antimicrobial peptide gene, defensin-1 (def-1), was used to assess immune system activation. We then checked whether the immune response includes changes in the expression of aging- and behavior-related genes, specifically vitellogenin (vg), juvenile hormone esterase (jhe), and insulin-like peptide-1 (ilp-1). We found a significant difference in survival rate between bees of different ages but carrying out the same tasks. Our results thus indicate that the bees' immune response is negatively affected by intrinsic senescence. Additionally, independent of age, foragers had a shorter lifespan than nurses after bacterial infection, although both were able to induce def-1 transcription. In the normal age demography colony, the immune system activation resulted in a reduction in the expression of vg, jhe and ilp-1 genes in foragers, but not in the nurse bees, demonstrating that age and behavior are both important influences on the bees' immune response. By disentangling the effects of age and behavior in the single-cohort colony, we found that vg, jhe and ilp-1 response to immune system stimulation was independent of behavior. Younger bees were able to mount a stronger immune response than older bees, thus highlighting age as an important factor for immunity. Taken together, our results provide new insights into how age and behavior affect the honey bee's immune response.
年轻的工蜂（0 到 2-3 周龄）在蜂巢内执行任务，包括照顾幼虫（哺乳），而年长的工蜂在接下来的 3-4 周内进行觅食任务，此时内在的衰老程序导致工蜂死亡。我们假设觅食者比哺乳蜂更难对免疫系统刺激做出反应，这种差异是由于觅食者的免疫反应效率低下。为了验证这一假设，我们使用了一种实验设计，使我们能够将时间年龄和行为状态（哺乳/觅食）分开。来自正常年龄群体的工蜂（其中工蜂随着年龄的增长自然从哺乳任务过渡到觅食任务）和单群体群体设置（由执行哺乳或觅食任务的同龄工蜂组成）的工蜂在接受细菌注射后进行了生存和免疫系统激活能力的测试。抗菌肽基因 defensin-1 (def-1) 的表达被用来评估免疫系统的激活。然后，我们检查免疫反应是否包括与衰老和行为相关基因表达的变化，特别是卵黄原蛋白 (vg)、保幼激素酯酶 (jhe) 和胰岛素样肽-1 (ilp-1)。我们发现不同年龄但执行相同任务的蜜蜂之间的存活率存在显著差异。因此，我们的结果表明，蜜蜂的免疫反应受到内在衰老的负面影响。此外，独立于年龄，在细菌感染后，觅食者的寿命比哺乳者短，尽管两者都能够诱导 def-1 转录。在正常年龄群体中，免疫系统的激活导致觅食者的 vg、jhe 和 ilp-1 基因表达减少，但哺乳者的基因表达没有减少，这表明年龄和行为都是蜜蜂免疫反应的重要影响因素。通过在单群体群体中分离年龄和行为的影响，我们发现 vg、jhe 和 ilp-1 对免疫系统刺激的反应独立于行为。年轻的蜜蜂能够比年长的蜜蜂产生更强的免疫反应，因此突出了年龄是免疫力的一个重要因素。总之，我们的研究结果提供了新的见解，说明年龄和行为如何影响蜜蜂的免疫反应。
