Mucosal Immunity (Exam 3) Flashcards
(25 cards)
3 special challenges of the GI regional immune system.
- tolerance of food antigen
- tolerance of commensal bacteria while respond to pathogens
- large surface area
What is the first layer of defense in regional immune systems? How does it prevent microbial invasion?
outer epithelial barrier
tight junctions
Give two examples of specialized lymphoid tissue distinct to the mucosal immune system.
- peyer’s patches
- tonsils
Regional immune systems have specialized cell types not abundant in other areas of the immune system. Provide this cell type for skin and for the GI tract.
skin: Langerhan’s cells
GI: M cells
What is the major function of M cells?
sample antigen from GI lumen for T cell activation
What two processes do M cells use to sample antigen from the GI lumen?
endocytosis & phagocytosis
What two locations are adaptive immune responses initiated in regional immune systems?
unencapsulated MALT
distant lymph nodes
Homing T cells in GALT back to the gut is mediated by:
vitamin A
When a GALT naive T cell in the gut is activated, it is exposed to ________ by dendritic cells. This allows it to express what two things for homing purposes?
retinoic acid (RA)
CCR9 + integrin a4B7 (alpha4beta7)
Activated T cells in GALT of the gut express CCR9, a chemokine receptor, and integrin a4B7 so it can return home after entering the circulation. What two molecules are expressed on endothelial cells that allow T cells to bind when it needs to come home?
CCL28 (ligand for CCR9)
MadCAM (adhesion molecule + ligand for a4B7)
List the 2 functions of Th17 cells in GI mucosal immunity.
- maintain epithelial barrier integrity
- protect from extracellular bacteria
Th17 cells function to maintain integrity of the GI epithelial barrier by producing what two cytokines?
IL-17
IL-22
What do Th17 cells produce that protects the GI tract from extracellular bacteria?
antibmicrobial peptides
If Th17 cells are overactive in the intestinal tract, what does this lead to?
irritable bowel disease (IBD)
In certain parts of the body, inflammation can be lethal so they have evolved to be more tolerant to foreign antigen. What is this concept called?
immune privilege
What parts of the body have immune privilege? (5)
brain, eye, testes, placenta, fetus
(T/F) One part of immune privilege is that the immune system has limited access to antigen in these regions of the body.
True
In areas with immune privilege, a mechanism to dampen inflammation is immunosuppressive _________.
cytokines
(T/F) Lymphocytes in immune privileged regions are rerouted to better serve other areas of the body but do not undergo cell death.
False - inactivated and/or killed
What two molecules are in the eye can be used to kill or suppress lymphocytes to limit inflammation?
Fas ligand
PD-1
(T/F) The blood-brain barrier is an example of immune privilege.
True
Which antibody functions in gut immunity?
IgA
What is the main function of IgA in gut immunity?
prevent both commensal and pathogenic microbes from invading bast epithelial lumen
________ migrate to the lamina propria of the gut and secrete IgA.
plasma cells
