Immunodermatology Dr. Sahu Flashcards
What is the function of MALT?
mucosa associated lymphoid tissue
mount mucosal responses to protect the body tracts
What is the function of SALT?
skin-associated lymphoid tissue
mount a cutaneous response to protect the skin
What provides the initial defense in MALT?
secretory IgA (SIgA) and innate leukocytes provide initial defense in MALT
How does MALT act to produce an immune response?
- M Cells in follicle associated epithelium of inductive site capture pathogens and convey them to mucosal APCs and T cells in domes covering B cell-containing lymphoid follicles
- DCs also capture ag via trnseptihelial dendrites
- Effector lymphocyte migrate to multiple mucosal effector site so provide coordinated protection via the common mucosal immune system
Immune responses in MALT are biased towards SIgA. Why could this be?
reduce inflammatory damage to fragile mucosae
Aggressive pathogens that that mucosal surfaces encounter may trigger responses from what immune cells
Th1/Th17 responses.
How does SALT activate immune responses?
- Keratinocytes provide an overlying physical barrier and secrete pro-inflammatory cytokines/chemokines that activate phagocytes and specialized APCs called Langerhan’s cells.
- Antigens are presented locally to activate epidermal memory T cells or are conveyed to naïve T cells in the local lymph node.
- Effector T cells generated can then home to skin sites under attack.
- While the skin is protected by Th1/Th2/Th17 responses initially, a persistent pathogen can trigger macrophage hyperactivation resulting in tissue damage.
Where are γδ T cells found and what is their function?
found in the skin
involved in skin immunosurveillance.
found in mucosal immune system
they work with activating NK receptor to recognize and kill injured enterocytes
What part of the mucosal barrier is rich in antimicrobial molecules?
the inner mucus layer
What part of the mucosal barrier is rich in antimicrobial molecules?
the inner mucus layer
What are some components of innate immunity of the mucosa? (first line of defense)
lysozyme
goblet cells
paneth cells
defenses
epithelial cells
Lysozyme has what actions?
Enzyme which hydrolyzes peptidoglycan, the main structural component of Gram positive bacterial cell walls; lysozyme can also be effective against Gram negative bacteria following damage to their outer membranes
Where is lysozyme present?
in secretions like tears sweat, saliva, sebum, gut mucosa where secreted by Paneth cells
What do goblet cells synthesize? Where do they synthesize these products?
secretory mucin and bioactive molecules in respiratory and intestinal tracts
What do Paneth cells secrete? Where are they located?
Secrete alpha defensins and bioactive molecules in the intestinal tract
What are Defensins? What do they do?
Human beta-defensins HBD
Small (35 - 40 aa) anti-microbial peptides rich in positively-charged arginine residues with 3 intra-chain disulfide bonds. Amphipathic in nature, they can penetrate microbial membranes and disrupt their integrity
HBD2 targets what?
gram -ve bacteria
HBD 3 targets what?
HBD3 gram +ve and gram -ve baceria
What does PRR stand for? What are they expressed by and what do they respond to?
Pathogen recognition receptors
Expressed by epithelial cells of enterocytes and respond to PAMPs (Pathogen-Associated Molecular Patterns)
Once PRRs recognize PAMPs they activate what to start their immune response? What do the epithelial cells in turn secrete?
activate NF-kB/other transcription factors
Epithelial cells produce chemokines, cytokines, and defensins
Where are MIC-A and MIC-B located and what do they express?
MIC-A and MIC-B— expressed on intestinal epithelial cells in response to cellular injury and stress
How do infected epithelial cells get killed through the MIC-A and MIC-B pathway?
What does GALT stand for what are its major components?
What is NALT and what are the major components?
Nasopharynx-associated lymphoid tissue.
