Biological and Environmental Sciences, School of Natural Sciences, University of Stirling, Stirling, UK.
Exp Gerontol. 2011 Nov;46(11):853-9. doi: 10.1016/j.exger.2011.07.004. Epub 2011 Jul 23.
Immune system effectiveness generally declines as animals age, compromising disease resistance. In Drosophila, expression of a variety of immune-related genes elevates during ageing; however how this is linked to increasing pathogen susceptibility in older flies has remained unclear. We investigated whether changes in the Drosophila cellular immune response might contribute to immunosenescence. Experiments studied fly cohorts of different ages and compared the numbers and activity of the circulating haemocytes involved in pathogen defence. In female wildtype Samarkand and Oregon R flies the haemocyte population fell by 31.8% and 10.2% respectively during the first four weeks of adulthood. Interestingly we detected no such decline in male flies. The impact of ageing on the phagocytic activity of haemocytes was investigated by injecting flies with fluorescently labelled microbes or latex beads and assessing the ability of haemocytes to engulf them. For all immune challenges the proportion of actively phagocytosing haemocytes decreased as flies aged. Whilst 24.3%±1.15% of haemocytes in one-week-old flies phagocytosed Escherichia coli bacteria or Beauveria bassiana fungal spores, this decreased to 16.7%±0.99% in four-week-old flies. This clear senescence of the Drosophila cellular immune response may underpin increased disease susceptibility in older flies.
免疫系统的效能通常随着动物年龄的增长而下降，从而降低其对疾病的抵抗力。在果蝇中，多种与免疫相关的基因的表达在衰老过程中会升高；然而，这与老年果蝇对病原体易感性的增加有何关联尚不清楚。我们研究了果蝇细胞免疫反应的变化是否可能导致免疫衰老。实验研究了不同年龄的果蝇群体，并比较了参与病原体防御的循环血球数量和活性。在雌性野生型 Samarkand 和 Oregon R 果蝇中，血球数量在成年后的前四周分别下降了 31.8%和 10.2%。有趣的是，我们没有在雄性果蝇中检测到这种下降。通过向果蝇注射荧光标记的微生物或乳胶珠，并评估血球吞噬它们的能力，研究了衰老对血球吞噬活性的影响。对于所有免疫挑战，随着果蝇年龄的增长，主动吞噬的血球比例下降。虽然在一周龄的果蝇中，有 24.3%±1.15%的血球吞噬了大肠杆菌细菌或球孢白僵菌真菌孢子，但在四周龄的果蝇中，这一比例下降到 16.7%±0.99%。这种明显的果蝇细胞免疫反应的衰老可能是老年果蝇易患疾病的原因之一。
