Gut Immunology Flashcards
(96 cards)
what does the gut-associated lymphoid tissue (GALT) consist of?
multi-follicular Peyer’s patches and isolated lymphoid follicles (ILF)
what is critical for the GALT and ILT development that in turn regulates the microbiota?
cross-talk between the host immune system and the microbiota
what are isolated lymphoid follicles (ILFs)?
they are single B-cell follicles that act as an inductive site for IgA production
what is the primary route by which the body is exposed to Ags (microbial and diet)?
the GALT
how do the Peyer’s patches and ILFs receive Ags since they lack afferent lymphatic vessels?
they receive Ags directly from the epithelial surfave and via Ag-transporting DCs
what is another way that microbes can cross the epithelium and enter the peyer’s patches?
through M cells, from which they are endocytosed by DCs in the subepithelial dome
Ag-loaded dendritic cells in the peyer’s patches interact with what to do what?
they interact with local lymphocytes to induce differentiation of T cells and T-dependent B cell maturation in the germinal center–> leads to the induction of the development of IgA producing plasma cells
what do goblet cells produce and how is their product organized?
they produce mucin, which is organized into a dense inner proteoglycan gel (inner mucous layer)
what cells continually sense the microbiota (MAMPs)?
enterocytes in the small intestine, colonocytes in the large intestine and specialized Paneth cells
what do the enterocytes, colonocytes, and Paneth cells induce the production of?
antimicrobial peptides (AMPs)
how does the secretory IgA maintain a peaceful bacteria-host interaction?
IgA does not activate complement, IgA does not activate phagocytes, and IgA is resistant to proteolysis
what is the major class of AMPs in the GI which represent innate immunity?
defensins
why is the inner mucous layer largely impervious to bacterial colonization or penetration?
due to its high density and high concentration of bactericidal defensins
describe the structure of defensins?
they have clusters of positively charged amino acid side chains and hydrophobic amino acid side chains
what do defensins cause in microbial membranes due to their structure?
membrane “wormholes” or pores
what are defensins produced by?
epithelial cells
what happens when commensal and pathogenic bacteria penetrate the enterocyte epithelial layer?
they are rapidly killed by macrophages in the lamina propria
what is lying over the peyer’s patches? and what happens if bacteria penetrate this?
a specialized follicle-epithelium, containing M cells. these bacteria are also rapidly killed by macrophages, but some bacteria can be picked up by DCs
once the DCs pick up antigen, where do they travel?
to the draining mesenteric lymph nodes
what do DCs that engulf bacteria induce?
IgA producing plasma cells
Although the DCs loaded with commensal bacteria can traffic to the mesenteric LNs, what do the LNs function as?
as a barrier, the loaded DCs cannot penetrate further to reach the systemic circulation
following activation, Ag-activated B and T cells leave the mesenteric LNs through the efferent lymph, enter the bloodstream at the thoracic duct and then do what?
home back to the intestinal mucosa
in the mesenteric lymph node, the dendritic cell interacts with a naive and does what?
stimulates their proliferation
where is the T cell differentiation taking place?
in the environment where stromal cells produce a significant amount of TGF-beta
