Gut-associated lymphoid tissues (GALT) are the key antigen sampling and adaptive immune inductive sites within the intestinal wall. Human GALT includes the multi-follicular Peyer’s patches of the ileum, the vermiform appendix, and the numerous isolated lymphoid follicles (ILF) which are distributed along the length of the intestine. Our current understanding of GALT diversity and function derives primarily from studies in mice, and the relevance of many of these findings to human GALT remains unclear. Here we review our current understanding of human GALT diversity, structure, and composition as well as their potential for regulating intestinal immune responses during homeostasis and inflammatory bowel disease (IBD). Finally, we outline some key remaining questions regarding human GALT, the answers to which will advance our understanding of intestinal immune responses and provide potential opportunities to improve the treatment of intestinal diseases.
Bibliographical noteFunding Information:
The authors thank Professor A. Mowat (Glasgow University) for valuable feedback during preparation of the manuscript. This work was supported by grants from the Lundbeck Foundation (R155-2014-4184), Denmark and the Gut Cell Atlas, an initiative funded by the Leona M. and Harry B. Helmsley Charitable Trust, US.