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Review
. 2016 Oct;186(1):1-9.
doi: 10.1111/cei.12821. Epub 2016 Jul 19.

The immunology of the vermiform appendix: a review of the literature

I A Kooij  1 , S Sahami  2 , S L Meijer  3 , C J Buskens  1 , A A Te Velde  1
Affiliations
Review

The immunology of the vermiform appendix: a review of the literature

I A Kooij et al. Clin Exp Immunol. 2016 Oct.

Abstract

This literature review assesses the current knowledge about the immunological aspects of the vermiform appendix in health and disease. An essential part of its immunological function is the interaction with the intestinal bacteria, a trait shown to be preserved during its evolution. The existence of the appendiceal biofilm in particular has proved to have a beneficial effect for the entire gut. In assessing the influence of acute appendicitis and the importance of a normally functioning gut flora, however, multiple immunological aspects point towards the appendix as a priming site for ulcerative colitis. Describing the immunological and microbiotical changes in the appendix during acute and chronic inflammation of the appendix, this review suggests that this association becomes increasingly plausible. Sustained by the distinct composition of cells, molecules and microbiota, as well as by the ever more likely negative correlation between the appendix and ulcerative colitis, the idea of the appendix being a vestigial organ should therefore be discarded.

Keywords: appendix; biofilm; immunology; inflammatory bowel disease.

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Figures

Figure 1
Figure 1
Transverse section of a healthy adult appendix. 1, mesoappendix; 2, muscularis externa; 3, submucosa; 4, lymphoid follicle; 5, mucosa and 6, lumen.
Figure 2
Figure 2
Appendiceal lymphoid follicle. Indicated are the distinctive areas of its most important constituents. 1, Dome epithelium: intra‐epithelial lymphocytes; 2, mixed cell zone: T‐lymphocytes, B‐lymphocytes, macrophages; 3, mantle zone: small B‐lymphocytes; 4, Germinal centre: centroblasts, centrocytes, follicular dendritic cells, macrophages; 5, T‐cell area: T‐lymphocytes, macrophages.
Figure 3
Figure 3
The process of biofilm formation, shedding and recolonization. Bacteria adhere to the surface. Biofilm formation and expansion by embedding bacteria within the mucin layer. Parts of the biofilm shed, which allows bacteria to relocate and recolonize (adapted from reference 42).
See this image and copyright information in PMC

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