GI - immunology Flashcards
what is the name of the lymph nodes found in the gut
peyer’s patches
what is the function of the ruffled membranes of M cells of payer’s patches
antigen sampling and absorption - endocytosis and phagocytosis
true/false
dendritic cells project themselves across epithelial membrane of gut to sample antigen in gut lumen
true
where are cytotoxic T cells (CD8) found in gut
epithelium (intraepithelial lymphocytes)
where are helper T cells (CD4) found in gut
lamina propria of gut cells
how are T cells in lamina propria activated
dendritic cells capture antigen at membrane, migrate to lymph nodes and present to T cells
what is MA
molecular address signal - binds to effector T cells which need to return to that area in the gut
what is chemokines role in gut immunity
direct migration of T cells through gut epithelium
why do HIV patients have mucosal immune dysfunction
loss of 70% of CD4+ T cells (helper/memory) in gut
where are IgA cells found in gut
lamina propria
how does IgA enter the epithelium from lamina propria
how does it enter gut lumen
endocytosis
exocytosis - while doing so can transport pathogens back to gut lumen
what is the purpose of the secretory component
allows IgA to persist in gut lumen for a awhile without being digested by proteolytic enzymes
how does IgA neutralise antigens
internalising them within a vesicle
what is the function of IgA
stops toxins and pathogens binding to gut epithelium
give 4 examples of when the mucosal immune system is dysregulated
primary immunodeficiency
allergy
coeliac disease
IBD
where do intraepithelial cells kill infected epithelial cells
basolateral side
what kind of immunodeficiency is HIV
acquired
what is XLA
X linked agammaglobulinaemia no B cells no IgG recurrent infection tx: immunoglobulin injections
what is a phagocyte respiratory burst
phagocytes produce reaction oxygen species (superoxide) to kill pathogens
what is chronic granulomatous disease
primary immunodeficiency
failure of phagocytes to produce superoxides for respiratory bursts
what is SCID
no B or T cells
constant pulmonary and GI infection
how is an allergy self-perpetuating
activated mast cells produce IL4 which stimulates B cells to produce more IgE
what genes trigger coeliac
HLA-DQ2
HLA-DQ8
(responsible for protein that activates T cell response)
what immune cells mediate coeliac
T cells
what occurs in coeliac
gluten specific T cells produce interferon gamma which triggers intraepithelial lymphocytes (CD8) to kill epithelial cells
what is the presentation of coeliac
abdominal pain bloating diarrhoea / steatorrhoea weight loss anaemia
what is seen in coeliac
flattened epithelium
villi atrophy
what is the gold standard Dx for coeliac
duodenal biopsy after positive tTG-IgA test
biopsy not in children
what is tTG
tissue transglutaminase
enzyme that modulates gluten by forming a complex with it when it enters the gut
the more gluten you eat the more tTG presented to B cells - more epithelial damage done
does the large intestine have villi
no just crypts
does the small intestine have villi
yes
villi and crypts
do both the small and large intestine have goblet cells
yes
where are paneth cells found
what do they do
small intestine
secrete defensives - antimicrobial peptide
where are peyer’s patches found
small intestine
where does antigen capture and activation occur in gut
mediated by dendritic cells
takes place in payer’s patches and across epithelium
what are M cells
part of epithelium covering Peyer’s patches
what are CCR7 and L-selectin
homing receptors which mediate T cell transport into payer’s patches
how do T cells become activated and reach the thoracic duct
activated by antigen bound dendritic cells
lose CCR7 so can no longer circulate
drain via mesenteric lymph nodes into thoracic duct
what is the function of a4-B7 integrin on T cell and MAdCAM-1 on endothelium
receptors aiding transport of effector immune cell out of gut
what Ig is most involved in humoral intestinal immune response
IgA
