Mucosal Immunity Flashcards
Why is the mucosa vulnerable?
Fragility and permebaility
Physiological functions of mucosal tissue?
Gas exchange
Food absorption
Sensory activities
Reproduction
Examples of mucosal tissues?
Mammary gland Salivary gland Kidnye Uterus/bladder/vagina Conjunctiva Trachea Lungs Intestine
Anatomical features of gut mucosal system?
Organised lymphoid structures unique to mucosal sites
Effector mechanisms of gut lymphocytes?
Activated/Memory T cells predominate
Natural effector/regulatory T cells- in organised tissues
Where is the Peyer’s patch?
Only in small intestine
What are Peyer’s atches covered in?
- Covered by an epithelial layer containing M cells which have membrane ruffles
- Takes up antigens by endocytosis/phagocytosis and transported across M cells in vesicles
- To dendritic cells which activate T cells
Special skill of dendritic cells?
Can reach through epithelial layer to capture antigen from lumen of gut
How many compartments is mucosal immune system?
2
Epithelium
Lamina propria
Immune cells of lamina propria?
- CCR9
- Plasma cell
- Dendritic cells
- Mat cells
- Macrophages
- C4 T cell
Immune cells of epithelial layer?
- CD8 T cell expressing alpha E:B7 integrin and CCR9
- Dendritic cells
What happens to T cells when they are activated by dendritic cells after they’ve encountered antigens?
Enter Peyer’s patch from blood vessels
Drain through lymph nodes to thoracic duct ad return to gut via bloodstream
Most common Ig in GI tract?
IgA (80%) the IgM the IgG
Dimeric
What can IgA do?
Neutralize pathogens and toxins also while internalized in endosomes
-Can also export toxins and pathogens from lamina propria while being secreted
Special T cells in Gut?
Intra-epithelial lymphocytes (IELs) 90% are T cells
What happens after virus infects mucosal epithelium cell?
Infected cell displays viral peptide to CD8 IEL via MHC class 1 -Activated IEL kills epithelial cell by Fas-dependant pathway
What happens when mucosal immunity is dysregulated in infections?
Infection crosses mucosa and fuses to dendritic cells which shuttle viruse to regional lymph nodes, infection spreads to CD4+ lymphocytes, these viral infected cells go into blood stream and disseminate across body
What is selective IgA deficiency?
Asymptomatic
Recurrent sino-pulmonary infection (coeliac disease x10)
What does CVID stand for?
Common variable Immuno-deficiency
What is CVID?
Recurrent Sino-pulmonary and GI infections (low IgA, M, G & E)
What does XLA stand for?
X linked agammaglobulinaemia
What is XLA?
Sinopulmonary and GI infection + devastating enteroviral infections (No B cells)
What is chronic granulomatous disease?
Staph aureus/ inflammatory granulomas
Pneumonia
Abcesses
Severe combined Immunodeficiency acronym?
SCID
What is SCID?
Defect in T & B cell immunity
What happens with IgE in allergies?
Secreted by plasma cells binds to mast cells which secrete signals to B cells to stimulate further IgE production.
During ingestion antigen diffuses into blood diseminating causing urticaria and anaphylaxis
Coeliac disease profile?
Genetically linked
Not an allergy
Loss of villi
Biopsy for gold standard diagnosis
2 examples of inflammatory bowel disease?
Crohn’s disease
Ulcerative colitis
What is Crohn’s disease?
Can affect any part from mouth to anus
- Focal and discontinuous inflammation with deep fissures +- granulomas
- Mediated by Th1 CD4+ T cells
What is ulcerative colitis?
Rectum and colon - starts in rectum and moves proximally
What do ulcerative colitis and Crohn’s disease both produce in large amounts?
Inflammatory cytokines IL-1, IL-6 and TNF alpha
Treatment of inflammatory bowel disease?
-NSAIDS (Non- specific anti-inflammatory and immunosuppressive drugs)
Steroids, azathioprine, methotrexate
