Mucosal Immunity Flashcards
How is direct contact between intestinal bacteria and epithelial cells minimized?
mucin and 1 layer of epithelial cells
In the mucosal system do activated/memory T cells prodeminate even in the absence of infection? What about Tregs?
yes
yes
What types of dendritic cells and macrophages dominate in the mucosal environment?
inhibitory macrophages and tolerance inducing dendritic cells
What are the 6 steps of antigens entering the digestive tract?
- M cells transports antigen across epithelium or DC extends detrite through epithelial tight junction into lumen
- Antigen taken up by APC
- Antigens are presented to lymphocytes
- lymphocytes leave mucosal site and travel to mesenteric lymph nodes then into the lym[p
- via the thoracic duct lymphocytes exit the lymph and enter circulation
- home to positions within the mucosal lamina propria throughout the body-including distant from origen antigenic encounter
- B cells in peripheral tissue proliferate and differentiate into IgA secreting plasma cells at effector sites
How do circulating lymphocytes home?
specific interactions of both adhesion molecules and chemokines
ex. alpah 4 beta 7=addressin to the gut
What are intraepithelial lymphocytes?
- distinct pop of lymphocytes
- mostly CD8
- found in gut epithelium
- may readily kill infected epithelial cells
What type of receptor recognizes endocytosed bacteria, what receptor recognizes bacteria entering the cytosol? What does this lead to?
endocytosed=TLRs
cytosol=NOD1 and NOD2
- epithelial cells to express a number of inflammatory cytokines, chemokines
- ->activates neutrophils, macrophages and dendritic cells
What is the most common primary immune deficiency?
selective IgA deficiency
What are some reasons to suspect selective IgA deficiency? Do you give IgA as treatment?
1) family history
2) high incidence of oral infection
3) frequent respiratory infections
4) chronic diarrhea
-no-people can produce anti-IgA in response and if completely lack IgA may trigger allergies or even anaphylactic shock
What does production of secretory IgA require?
plasma cells in the lamina propria and epithelial cells of the mucosa
What does dimeric IgA bind to after it is produced by the plasma cells?
polymeric immunoglobulin receptor (pIGR) on the basolateral surface of the mucosal epithelial cells
What happens to the remaining fragment after pIGR is cleaved during transport?
covalently bound to dimeric IgA
What are the only immunoglobulins capable of binding and being transported by the pIgR?
polymeric immunoglobulins
dimeric IgA or pentameric IgM
What does secretory IgA do?
binds bacteria and viruses and prevents their adherence and invasion into mucosal tissue
What does intraepithelial IgA do?
may contribute to intracellular viral intactivation
