Department of Biological Sciences, Virginia Tech, Blacksburg, VA, USA.
Avian Pathol. 2020 Aug;49(4):342-354. doi: 10.1080/03079457.2020.1753652. Epub 2020 May 18.
Leukocyte differentials are a useful tool for assessing systemic immunological changes during pathogen infections, particularly for non-model species. To date, no study has explored how experimental infection with a common bacterial pathogen, (MG), influences the course and strength of haematological changes in the natural songbird host, house finches. Here we experimentally inoculated house finches with MG isolates known to vary in virulence, and quantified the proportions of circulating leukocytes over the entirety of infection. First, we found significant temporal effects of MG infection on the proportions of most cell types, with strong increases in heterophil and monocyte proportions during infection. Marked decreases in lymphocyte proportions also occurred during infection, though these proportional changes may simply be driven by correlated increases in other leukocytes. Second, we found significant effects of isolate virulence, with the strongest changes in cell proportions occurring in birds inoculated with the higher virulence isolates, and almost no detectable changes relative to sham treatment groups in birds inoculated with the lowest virulence isolate. Finally, we found that variation in infection severity positively predicted the proportion of circulating heterophils and lymphocytes, but the strength of these correlations was dependent on isolate. Taken together, these results indicate strong haematological changes in house finches during MG infection, with markedly different responses to MG isolates of varying virulence. These results are consistent with the possibility that evolved virulence in house finch MG results in higher degrees of immune stimulation and associated immunopathology, with potential direct benefits for MG transmission. House finches show a marked pro-inflammatory response to infection. Virulent pathogen isolates produce stronger finch white blood cell responses. Among birds, stronger white blood cell responses are associated with higher infection severity.
白细胞分类是评估病原体感染期间系统免疫变化的有用工具，特别是对于非模式物种。迄今为止，尚无研究探讨实验性感染常见细菌病原体（MG）如何影响天然鸣禽宿主家雀血液变化的过程和强度。在这里，我们用已知毒力不同的 MG 分离株对家雀进行了实验接种，并在整个感染过程中量化了循环白细胞的比例。首先，我们发现 MG 感染对大多数细胞类型的比例有明显的时间效应，感染过程中异嗜粒细胞和单核细胞的比例明显增加。淋巴细胞比例也显著下降，但这些比例变化可能只是其他白细胞相关的增加所驱动的。其次，我们发现分离株毒力有显著影响，与假处理组相比，感染毒力较高的分离株的鸟类中细胞比例变化最大，而感染毒力最低的分离株的鸟类几乎没有可检测到的变化。最后，我们发现感染严重程度的变化与循环异嗜粒细胞和淋巴细胞的比例呈正相关，但这些相关性的强度取决于分离株。总的来说，这些结果表明家雀在 MG 感染期间发生强烈的血液变化，对毒力不同的 MG 分离株有明显不同的反应。这些结果与家雀 MG 进化的毒力导致更高程度的免疫刺激和相关免疫病理学的可能性一致，这可能对 MG 传播有直接益处。家雀对 感染表现出明显的促炎反应。毒力病原体分离株产生更强的 Finch 白细胞反应。在鸟类中，更强的白细胞反应与更高的感染严重程度相关。
