2-30 Gut Immunity Flashcards Preview

Unit 2 > 2-30 Gut Immunity > Flashcards

Flashcards in 2-30 Gut Immunity Deck (10):
1

What features characterize mucosal immunity?

  • Proactive approach
  • Mucus barrier
  • Large population of resident immune cells
  • Macrophages resident in mucosal tissues do not initiate inflammation in response to penetration of the epithelial layer
  • Less T cell activation

2

Which anatomical structures contribute to mucosal immune surveillance?

Waldeyer’s Ring: adenoids, palatine, and lingual tonsils form a ring of lymphatic tissue around the alimentary canal

Appendix: rich in lymphoid follicles, located at junction of large and small intestine

3

Which microscopic structures contribute to immune surveillance?

Throughout the intestinal walls are microscopic immune aggregates (Peyer’s patches of T and B lymphocytes and dendritic cells) that carry out more localized surveillance and response activities.

Potential antigens pass through M (microfold) cells via transcytosis and are transported to Peyer’s patches to be evaluated by dendritic cells.

4

What cells direct the gut immune response, and what do they do?

CD103+ dendritic cells take up antigens from digested food, commensal microorganisms, and potential pathogens, and present them to antigen-specific T cells. CD103+ DCs direct the immune response in one of two possible directions:

  1. Soluble proteins/food macromolecules → oral tolerance
  2. Microbial Ags → antibody response: CD4+ T cells activated → pair w/ antigen-specific B cells → provide T-cell assistance for Ab production

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5

What is oral tolerance?

Achieved when CD103+ DCs encounter soluble proteins or other macromolecules derived from foods.

Ag-specific T cells reactive to fragments of these harmless molecules are rendered anergic (through lack of co-stimulation) or can be induced to become Tregs through DC secretion of IL-10. No adaptive response occurs, and no Ab is generated against the Ag.

6

How are lymphocytes directed to GI mucosal tissues to fight infection?

Lymphocyte cell surface receptors (low [CCR7] → high [integrin α4:β7] and [MAdCAM-1]) direct naïve and activated cells to proper locations.

7

What are some immune cells found in a healthy intestine?

Because of immune cell homing to mucosal tissues, there is a large population of resident immune cells in healthy gut tissues.

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8

How does the gut protect its mucosal surfaces?

Secreted immunoglobulins.

Activated B cells that have effectively homed to the mucosal lamina begin to secrete antigen-specific IgM. Most undergo affinity maturation and switch isotypes to produce IgA antibodies (IgA1 and IgA2), which are actively transported across the epithelium and into the lumenal mucus.

9

What are the two kinds of IgA?

IgA1 looks like an 'L'--for "long" hinge. Better flexibility and binding, but susceptible to proteolytic cleavage. Predominates among lower bacterial numbers.

IgA2 looks like an inverted 'S'--for "short" hinge. Less susceptible to cleavage, but worse binding. Found among higher bacterial concentrations.

In its secreted form, IgA is dimeric and joined by a J chain.

10

What best resolves parasitic worm infections?

TH2 subset of CD4+ helper T cells

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