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Mucosal Immunity

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isabellepjk's version from 2017-04-10 10:43

General

Question Answer
What type of mechanisms for immune defense are found on mucosal surfaces?Acquired and innate
What are 5 exampes of innate protective mechanisms at mucosal surfaces ?Defensins sereted by intestinal epithelial cells which prevent bacteria from entering the crypts of intestinal mucosa
Low pH and flushing action of the urinary system
Lysozyme in gastric and intestinal mucosa (antibacterial, antiviral)
Mucociliary blanket of the resp system
Resident flora of on mucosal surfaces
What are the two categories of lymphoid tissues with acquired immunity?Inductive and Effector
What happens at the inductive sites of mucoid lymphoid tissues?
Which tissues have these?
Sites where Ags are encountered, processed, and immune responses (humoral and CMI) are initiated.
Examples: Tonsils, appendix, GALT, BALT, and Peyer's Patches (INDUCE/INITIATE an immune response)
What happens at the effector sites of mucoid lymphoid tissues?Abs and CM responses are carried out --> they are actually doing their job (Have an EFFECT)
IgA secretion
Where does Ab class switching occur?Peyer's Patches
Where does Ab secretion occur?in the effector areas of the vili
Specifically, what do the Effector B and T lymphocytes do in the effector site of mucoid lymph tissues?If they are generated in one location, they can can circulate to distant sites to carry out their function.

THEN, they will secrete Ab (B cells: typically IgA-Abdomen, airway) specific to the Ag that stimulated them in the intestinal lymphoid tissues
Why is the movement of IgA secreting B cells from the intestine to the mammary gland important?
How does it work?
It provides a route through which INTESTINAL IMMUNITY can be transferred to the newborn through milk.
Oral administration of Ag to a pregnant animal will results in the appearance of IgA Abs in the milk. The intestine of a new born drinking milk will be flooded by Abs directed against intestinal pathogens
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Acquired Protective Mechanisms

 

Question Answer
By which 2 mechanisms are mucosal surface protected?CMI and Ab
How does IgA act on mucosal surfaces?Immune exclusion
What is immune exclusion?IgA prevents the adherence of bacteria and viruses to epithelial surface (also its most important function)
Where is IgA found?Colostrum, intestinal fluid, milk, nasal secretions, saliva, tracheal secretions, and urine.
Where is IgA synthesized and by whom?synthesized and secreted by plasma cells, as a dimer, in the intestinal submucosa
How does IgA get from the intestinal submucosa to the intestinal epithelial surfaces?-IgA is secreted and synthesized by plasma cells in the intestinal submucosa as a dimer.
- The dimeric IgA binds to a receptor (poly-Ig) on the basal surface on enterocytes.
- The poly-Ig-receptor-IgA complex is endocytosed and transported across the enterocyte.
- When it reaches the luminal surface, the vesicle fuses with the plasma membrane and exposes the IgA to the intestinal lumen.
- Part of the poly-Ig molecule is cleaved off , leaving the receptor peptide chain still attached to the IgA (receptor peptide = secretory piece)
- DIMER + POLY-IG-RECEPTOR --> ENDOCYTOSIS --> IGA EXPOSED TO LUMEN --> POLY-IG CLEAVED OFF = RECEPTOR PEPTIDE (SECRETORY PIECE STILL ATTACHED)
What is a secretory piece?When the Poly-Ig-Receptor-IgA complex reaches the luminal surface, IgA is exposed to the intestinal lumen.
Then, part of the poly-Ig receptor molecules is cleaved off and part of the receptor peptide is still attached to the IgA. The receptor peptide chain is the Secretory Piece
What is secretory IgA?
What is important about it?
Dimeric IgA bound to the secretory piece.
It is resistant to proteases within the mucus at the surface of epithelium
What is important about the secretory IgA?It is resistant to proteases within the mucus at the surface of epithelium
What is the rule exception regarding Ab?Rule is normally that Ab does not get into cells, exception is that since IgA is transported through enterocytes, it can act INSIDE the enterocytes and bind viral proteins inside these cells, interrupting viral replication.
What is the main class (and minor) of Ab that uses Immune elimination?IgE is the main, but IgG is also there sometimes (Elimination for IgE)
What is immune elimination?
Which Ig classes mediate it?
Destroying the Ag that penetrates the mucosal barrier, mediated mostly by IgE but IgG too
How does immune elimination work?If invading organisms can evade the IgA and get access to the tissues, IgE is triggered.
There is rapid degranulation of mast cells with the release of vasoactive molecules into the tissues leading to inflammation, increased vascular permeability, and fluid leakage between enterocytes, AND THEREFORE, fluid entering the lumen.
What are the specifics of the IgE mast cell binding? IgE attaches to mast cells via the Masts Fc receptor which is specific for the Fc region of the IgE Ab.
FAb region is the region that is sticking out now so it can bind the Ag.
What is an example of an immune elimination process?Parasites invading intestinal mucosa!
With fluid and inflammation, intestinal motility increases and is sufficient to force that parasite to disengage and be flushed out
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