Immunity Flashcards
What is a Peyer’s patch?
A specialised lymph node in the small intestine
what are peyer’s patches covered by?
epithelial layer
what does the epithelial layer covering peyer’s patches contain?
specialised cells called M cells which have characteristic membrane ruffles
how do M cells take up antigens?
by endocytosis and phagocytosis
how are antigens transported across M cells?
in vesicles and released at the basal surface
what happens once the antigen crosses the M cell?
antigen is bound by dendritic cells and activate T cells.
how else might an antigen be captured from the lumen in the gut?
dendritic cells can extend processes across the epithelial layer and capture antigens.
How do T cells enter Peyer’s patches?
from blood vessels, directed by the homing receptors CCR7 and L-selectin.
what happens to T cells once they are activated by dendritic cells in the peyer’s patches?
drain via mesenteric lymph nodes to the thoracic duct and return to the gut via the blood stream.
How does IgA leave the cell?
by endocytosis
what can secreted IgA on the surface do?
- bind and neutralise pathogens and toxins
- bind and neutralise antigens internalised in endosomes
- export toxins and pathogens from lamina propria while being secreted
What are the lymphocytes that lie within the epithelial lining of the gut called?
Intra-epithelial lymphocytes (IELs)
what cells are mostly found in the IELs?
CD8 positive T cells
How do infected cells display viral peptides to CD8 IEL?
via MHC class I
how does activated IEL kill infected epithelial cells?
by perforin/granzyme and Fas-dependent pathways
