Immunology of the GI tract Flashcards
in which part of the GI tract are lymphocytes and plasma cells located?
epithelia and lamina propria
the epithelia and lamina propria contain what immunological cells?
lymphocytes and plasma cells
what is the most abundant Ig in the body?
IgA
what is the big difference between mucosal immunity and normal immunity in terms of duration?
mucosal immunity does not last as long
is there immune induction at effector cell sites? what are these sites?
no
lymphocytes in epithelia and lamina propria
what GALT is important in promoting IgA production and CTL responses?
Peyer’s patches
in which layer of the GI tract are Peyer’s patches located?
lamina propria
where are M cells found? what is their role?
dome epithelium of Peyer’s patches
transfer antigens from gut lumen to lymphoid tissue, which are then presented to T helper cells by APCs
M cells interact directly with which immune cells?
APCs
Peyer’s patches are covered by epithelium consisting of what special cell type?
M cells
what is the morphology of M cells?
ruffled, micro-folded membranes
which microbes exploit M cells to get into gut wall?
salmonella, yersinia, listeria, shigella
salmonella, yersinia, listeria, and shigella invade the gut wall through what mechanism?
bacterial proteins bind cellular receptors to induce uptake
phagocytosis and macropinocytosis via M cells
intraepithelial lymphocytes are composed primarily of what immune cell?
CD8 T cells
cells in the lamina propria are composed primarily of what immune cell?
CD4 T cells
pre-plasma cells leave peyer’s patches via what channels?
lymphatic capillaries
how do pre-plasma cells get to the lamina propria after leaving the peyer’s patches?
migrate via mesenteric lymph channels and thoracic duct
what molecules play a role in the homing of pre-plasma cells to the lamina propria?
addressins
how does IgA get to the mucosal surface?
binds to poly-Ig receptors and transported across cell and delivered to mucosal surface
which IgA is dimeric? which is monomeric?
dimeric - mucosal
monomeric - serum
how does IgA1 differ from IgA2?
IgA1 can fix complement via the alternative pathway
how does IgA prevent binding of microbes to epithelia and facilitate expulsion?
opsonize small pathogens for phagocytosis
eosinophil degranulation for parasites - eosinophils have receptors for IgA
what subtype of T cells make up a significant % of epithelia-associated T cells in the GI tract?
gamma delta
what are the antigens for gamma delta T cells in the GI tract?
heat shock proteins, nucleotides, phospholipids
what comprises secretory component?
a piece of a poly-Ig receptor
what is the role of secretory component?
protects IgA from being broken down by proteolytic enzymes
what supplies the secretory component?
mucosal cell itself
where are mast cells located?
deep to epithelia that is exposed to environment
what is the normal immune function of mast cells?
IgE mediated defense against parasites
what is oral tolerance?
immune system is told to not respond to certain antigens
a way to keep immune system’s hands off of things you eat in order to avoid an undesirable immune response
what occurs following high dose of oral antigen?
clonal deletion of antigen-specific lymphocytes (they die)
what occurs following low dose of oral antigen?
clonal anergy (unresponsiveness) and regulatory T cells suppress immune responses
regulatory T cells developed in GALT can migrate systemically
what is the most common immunodeficiency in humans?
selective IgA deficiency
selective IgA deficiency is associated with increased risk of what condition?
autoimmune disease
reactions to food proteins are usually the result of what Ig?
IgE
what is the response of intraepithelial lymphocytes following gluten sensitive enteropathy?
10x-15x increase in T cell reaction
what is the result in the lamina propria following gluten sensitive enteropathy?
increase in TCR bearing CD4 and CD8 T cells
untreated or partially treated gluten sensitivity enteropathy can lead to what conditions?
GI lymphoma, carcinoma
crohn’s disease
inflammatory and granulomatous lesions commonly involving terminal ileum and ascending colon
what is the antibody therapy for crohn’s disease?
infliximab
what molecule plays a large role in crohn’s disease?
TNFa
how does ulcerative colitis begin? secondary?
diffuse lymphocyte rich infiltrate
granulocytic inflammatory cells during abscess formation
how does crohn’s disease begin?
classic macrophage containing granulomatous lesions
what is the most common cause of pernicious anemia? what is the result?
autoantibodies against IF
B12 cannot be transported into circulation
