Centre d'Immunologie de Marseille-Luminy, Aix-Marseille Université, INSERM, CNRS, Marseille, France.
Maurice Müller Laboratories (Department for Biomedical Research), Universitätsklinik für Viszerale Chirurgie und Medizin Inselspital, Murtenstrasse 35, University of Bern, 3010 Bern, Switzerland.
Semin Immunol. 2018 Apr;36:31-44. doi: 10.1016/j.smim.2018.02.005. Epub 2018 Mar 2.
Biological redundancy ensures robustness in living organisms at several levels, from genes to organs. In this review, we explore the concept of redundancy and robustness through an analysis of the caecal appendix, an organ that is often considered to be a redundant remnant of evolution. However, phylogenic data show that the Appendix was selected during evolution and is unlikely to disappear once it appeared. In humans, it is highly conserved and malformations are extremely rare, suggesting a role for that structure. The Appendix could perform a dual role. First, it is a concentrate of lymphoid tissue resembling Peyer's patches and is the primary site for immunoglobulin A production which is crucial to regulate the density and quality of the intestinal flora. Second, given its shape and position, the Appendix could be a unique niche for commensal bacteria in the body. It is extremely rich in biofilms that continuously shed bacteria into the intestinal lumen. The Appendix contains a microbiota as diverse as that found in the colon and could replenish the large intestine with healthy flora after a diarrhea episode. In conditions of modern medicine hygiene, and people live healthy without their appendix. However, several reports suggest that the effects of appendectomy could be subtler and associated with the development of inflammatory conditions such as inflammatory bowel disease (IBD), heart disease but also in less expected disorders such as Parkinson's disease. Lack of an Appendix also predicts a worsen outcome for recurrent Clostridium difficile infection, which is the first nosocomial infection in hospitals. Here, we review the literature and in combination with our own data, we suggest that the Appendix might be redundant in its immunological function but unique as a reservoir of microbiota.
生物冗余性确保了从基因到器官的多个层次的生物体的稳健性。在这篇综述中，我们通过分析盲肠阑尾这一经常被认为是进化冗余遗迹的器官，探讨了冗余性和稳健性的概念。然而，系统发生数据表明，阑尾是在进化过程中被选择的，一旦出现就不太可能消失。在人类中，阑尾高度保守，畸形极为罕见，这表明该结构具有一定的作用。阑尾可能具有双重作用。首先，它是类似于派尔集合淋巴结的淋巴组织的浓缩物，是产生免疫球蛋白 A 的主要场所，这对于调节肠道菌群的密度和质量至关重要。其次，考虑到其形状和位置，阑尾可能是体内共生细菌的独特栖息地。它富含生物膜，不断将细菌脱落到肠腔中。阑尾中的微生物群与结肠中的微生物群一样多样化，并且可以在腹泻发作后为大肠补充健康的菌群。在现代医学和卫生条件下，人们在没有阑尾的情况下也能健康生活。然而，有几项报告表明，阑尾切除术的影响可能更为微妙，并与炎症性疾病（如炎症性肠病，IBD）、心脏病的发展有关，甚至与不太预期的疾病（如帕金森病）有关。缺乏阑尾也预示着复发性艰难梭菌感染的预后恶化，这是医院中第一种医院获得性感染。在这里，我们回顾了文献，并结合我们自己的数据，提出阑尾在其免疫功能方面可能是冗余的，但作为微生物群的储库却是独特的。
