Mucosal Immunology Flashcards
What are the three structures that form a ring of lymphoid tissue around the entrance to the pharynx?
1-Palatine tonsil
2-Lingual tonsil
3-Pharyngeal tonsil (called adenoids when infected)
What main two types of immune cells are found in the epithelial lining of the GI tract
1-T cells
2-B cells
What are the 2 main places that immune cells are found in the gut?
1-Peyers patch
2-Intraepithelial lymphoid follicles (ILF)
Appearing as clusters of 3 or more large lymphoid aggregates, what structure has large B cell follicles with T cell area surrounding it (mainly CD4), Is not served by afferent lymphatics, and is responsible for much of the IgA in the gut?
Peyers Patch
*Antigen sampling is controlled by M cells
Which immune structure is 100-200 clusters of lymphocytes in the small intestine that consist of 70% B cells, 20%CD4 T cells and 10% CD11c DC, have overlying M cells, and function as inductive sites for mucosal immune response?
Intraepithelial lymphoid follicles (ILF)
What is the major different between mouth and gut epithelium?
- Mouth is stratified squamous epithelium
- Gut is single layered epithelium
What are the 4 major cell types of the gut immune system?
1-Adsoprtive epithelial cells (IECs or enterocytes)
2-M (microfold) cells
3-Goblet cells
4-Paneth cells
Which cells increase the surface area of the intestine, possess surface glycocalyx, are covered in mucus, and make up most of the intestinal epithelia?
Absorptive epithelial cells (IECs or enterocytes)
Which cells are critical for antigen sampling, have no vili, have extensively folded basal membrane, do not secrete mucus or digestive enzymes and lack a surface glycocalyx?
M (microfold) cells
The transportation of antigen across M cells in vesicles which are then released at the basal surface to be bound by dendritic cells is called what?
Transcytosis
Which cells make antimicrobial peptides such as defensins?
Paneth cells
*a-defensins in the small bowel by paneth cells, B-defensins in the colon by absorptive epithelial cells in the intestinal crypts
What two places in the gut to Dendritic cells “hangout”?
1-Within Peyers patches
2-Within the lamina propria
What are the two functional subgroups of dendritic cells?
1-Effector dendritic cells (CD11b+CX3CR1+)
2-Regulatory dendritic cells (CD103+CX3CR1-)
Effector dendritic cells stimulate what?
Protective effector T cell response
Regulatory dendritic cells stimulate what?
Regulatory T cell responses that suppress immunity against ingested antigens and commensal organisms
90% of IELs are T cells. 80% of them are what type of T cells?
CD8+
*in systemic compartment CD4 outnumber CD8 3:1
CCR9 and aeB7(CD103+) integrin is expressed on T cells in the gut and bind what?
E-cadherins on epithelium
*a4b7 is the typical integrin expressed
What cells have an invariant TCR and respond to antigens presented by non-classical MHC molecule MR1 on B cells?
Mucosal Invariant T cells (MAIT)
Which cells have multiple types, based on their cytokine profile (ILC1, 2, 3) and are a fairly new population of cells that look like lymphocytes but have innate like qualities?
Innate lymphoid cells (ILCs)
*can present antigens
What are the two groups of CD8+ IELs?
1-Type A- CD8ab-classic
2-Type B- CD8 αα homodimers (can have αβ TCR or γδ TCR)
What do activated IEL used to kill infected epithelial cells?
Perforin/granzyme and Fas-dependent pathways
Wha binds MIC-A and MIC-B that is expressed on stressed epithelial cells?
NKG2D
*CD8α:α homodimers also bind TL
Secretion of what allows Dendritic Cells to induce differentiation of naive T cells into FoxP3+ regulatory T cells as well as gut homing molecules CCR9 and a4B7 and holding CD103+ cells in anti-inflammatory state?
Retinoic acid
*metabolism of Vitamin A into retinoid acid using retinol dehydrogenase
Present in mucosal secretions as a polymer, which antibody has two isotopes (1 and 2) and makes up 60-70% of the total antibody secretions each day?
IgA
*occurs in the absence of a pathogen and is driven by food and commensal bacteria
Which two antibody types are transported across the epithelia?
IgA/IgM
*IgAs do not induce complement or opsonize so it does not induce inflammation. also interferes with IgG ability to activate complement
The secretion of which antibody into the lumen binds and blocks bacterial adhesion to receptors on epithelial cells and enhances antimicrobial effects of innate humoral factors (lactoferrin/lysozyme)?
IgA
