immuno Flashcards
Which antibody protects our gut mucosa from foreign antigens?
secretory IgA
What does oral tolerance depend on?
microbial components and dietary factors such as fiber, vitamin A and lipids
Why is breastfeeding important to maintain months after birth?
it promotes oral tolerance
What causes food allergy?
removal of oral tolerance due to inappropriate interactions bn genes and environment
What factors contribute to your gut microbiota?
- mode of delivery (natural birth vs c section)
- infant diet
- antibiotics
- probiotics
- physical environment
Why is a normal gut microbiota important?
healthy gut microbiota leads to immune tolerance, intestinal homeostasis, and healthy metabolism.
disruption of the gut microbiota is associated w diseases (immune, intestinal and metabolic diseases)
What are the 4 GALTs?
tonsils and adenoids, Peyer’s patches, isolated lymphoid tissues, and appendix
What causes proliferation of epithelial cells in the gut?
when microflora destroys bacteria, components of the bacteria get absorbed into the epithelium and lymphoid tissue, and allows for proliferation
What is the significance of mature isolated lymphoid follicles?
- only B cell generating
- utilize dendritic cells instead of afferent lymphatics
- produce IgA antibodies
- important for activation of B cells
What do M cells do?
take antigens from the outside and bring them inside to be recognized by Peyer’s patches
if B cells are activated in the Peyer’s patch or mesenteric lymph node, where must they go?
systemic blood circulation
Which cytokine makes IgA?
TGF-B
Abnormal activation of Th1 cells causes what?
inflammation -> Crohn’s Disease
Abnormal activation of Th2 cells causes what?
Allergy/Food adverse reactions
Activation of Treg cells causes what?
homeostasis/tolerance
What are the components of the mucosal firewall?
- mucus is the primary barrier
- AMPs produced by epithelial cells
- macrophages across the barrier eliminate pathogens that passed through
- dendritic cells produce IL-6/TGF-B go to mesenteric LN, which leads to differentiation of Treg cells
- DCs also activate Th17 which upregulate AMPs
What does dysbiosis lead to?
dysregulation of immune system and inflammation
What is the relationship between microbiota, the immune system and diet?
malnutrition leads to decreased immune function, which leads to infection with enteropathogens, which leads to impaired absorption, and the cycle repeats
How do undigested dietary carbs lead to homeostasis?
they produce SCFAs, which can lead to accumulation of Treg cells, production of mucus and also support IgA mediated responses to gut pathogens,
What is the significance of acetate, butyrate, and PSA?
acetate results in Treg cells
Butyrate acts on Treg cells or modulates DC function to enhance their treg inducing ability
PSA also directly acts on Tregs through TLR2 to promote Treg function by enhancing expression of IL-10 and TGF-B
What is oral tolerance?
Oral tolerance is an active process of local and systemic immune unresponsiveness to orally ingested antigens such as food.
What three groups of immune cells play a role in oral tolerance?
macrophages, DCs and Treg cells
What are the two main adverse food reactions to non toxic reactions
non-immune mediated (food intolerance) and immune mediated (Food allergy)
What are the responses of non immune mediated reaction?
pharmacological, enzymatic, irritant, psychosomatic
What are the responses of immune mediated reaction?
IgE mediated (type 1 hypersensitivity) and non IgE mediated (type 3 or type 4)
what are the events of initiation of allergy?
an allergen contacts DCs, which cause naive T cells to release IL-4, and allow differentiation into Th2
Th2 releases IL-4 to induce IgE
also releases cytokines to activate basophils, eosinophils and mast cells
What do mast cells release?
proteases, histamine and cytokines IL-1B and TNF-a
how do mast cells activate complement?
histamine released from mast cells increase vascular permeability and the exudation contains C3 and C5,
Tryptase which is also released, acts on C3 and C5 and generates C3a and C5a, which further activate mast cells
How do vitamins suppress inflammation?
they activate Treg cells
What food factors contribute to food allergy?
high fat diet and medium chain TG lead to innate activation by allergens and Th2 (allergic effector)
what is the most common food allergy?
milk allergy
How can peanuts and nuts cause activation of complement?
they cause production of C3a, which sitmulates macrophages, basophils and mast cells to produce PAF and histamine
What are anaphylactic reactions in the GI? airways? blood vessels?
diarrhea and vomiting (expulsion of GI contents)
expulsion of airway contents (coughing)
edema, inflammation, increased lymph
what is the mechanism of anaphylactic reactions?
sudden release of mediators, as a result of events mediated by IgE
what is the mechanism of Type IV non IgE mediated food allergy?
Type IV hypersensitivity; T cell mediated
causes macrophage activation and inflammation induced by cytokines that are produced by CD4 Th1 and Th17 cells or CD8 CTLs
what is the mechanism of Type III non IgE mediated food allergy?
classical complement cascade recruit macrophages
What causes food intolerance?
genetics, absence of enzymes, IBS, food poisoninG
What is the mechanism of celiac disease?
gluten acts as an antigen, which bind to HLA class II. Gluten specific Th1 cells are generated and causes type IV hypersensitivity
