9. Mucosal Immunity Flashcards
MALT
Mucosa associated lymphoid tissue
NALT
Nasopharynx-associated lymphoid tissue
GALT
Gut associated lymphoid tissue
Main task of MALT
Complete exclusion of various infectious agents and other antigens in the intestinal lumen, local or systemic immune response, induction of tolerance
Where can we find M cells?
In the epithelium above the Peyer patches
The mucosal immune system consists of two distinct compartments
- The epithelium
2. Lamina propria
How does IELs function?
- Virus infects mucosal epithelium cell
- Infected cell displays viral peptide to CD8 IEL via MHC class I
- Activated intraepithelial lymphocytes kills infected epithelial cell by perforin/granzyme and Fas-dependent pathways
Two functional sites of GALT
- Inductive site (Peyers patch)
2. Effector site (Immune exclusion)
IgA class switching
- TD: Will result in high affinity IgA
2. TI: Will result in low affinity IgA
Checkpoints for the epithelial mucosal system
- Soluble/particulate PAMPs
- Dead/alive
- Pathogen/non-pathogen
- Harmless/harmful colonization of epithelial surfaces
Direct tissue damage by pathogens
- Exotoxin production (extracellular pathogens)
- Endotoxin (intravesicular pathogens)
- Direct cytopathic effect (viruses)
Indirect tissue damage by pathogens
- Immune complexes (strep.)
- Anti-host Ab (strep.)
- Cell mediated immunity (eg. herpes)
Where can we find GALT?
Tonsils, appendix, Peyers patches
Function of M cells
- M cells take up Ag by endocytosis and phagocytosis
- Ag transported across M cells in vesicles -> released at the basal surface
- Ag bound by DCs -> activate T cells
IEL are what kind of cells?
CD8 positive cytotoxic T cells
