Immunology Flashcards
Define autoimmunity.
A misdirected immune response against host tissue. It is a complex interaction between genetic susceptibility and environmental exposure.
What is the difference between a food allergy and a food intolerance?
Food allergy -> An overreaction of the immune system to a protein allergen (food). Involves TH2 activation, IgE production and mast cells, eosinophil, basophil accumulation.
Food intolerance -> Difficulty digesting foods and doesn’t involve the immune system. No IgE production, protective IgA production.
What is the process of T cell selections part of central tolerance?
Positive selection -> selects T cells capable of interacting with self MHC molecules.
Negative selection -> removes T cells that strongly bind MHC+ self peptides.
Occurs in the thymus.
What are Treg cells?
Induced by dendritic cells and recognise self antigens. They release cytokines that limit inflammation (IL-10). They inhibit activation of CD4+ T cells.
What happens if the B cell reacts to self antigens in the central tolerance test?
High affinity to self antigens -> Receptors are edited until the B cell no longer binds to self-antigens or apoptosis.
Low affinity -> decreased receptor expression and signalling -> anergy, where the B cell is present but doesn’t respond.
How is lactose normally broken down in the small intestine?
Lactase enzyme breaks down lactose into glucose and galactose.
What happens to lactose if it can’t be broken down in the small intestine?
It is fermented by the colonic microbiome to produce short chain fatty acids and gas (H, CO2, methane).
What type of autoimmune disease is Coeliac?
TH1 autoimmune disease which doesn’t involve IgE.
What sort of reaction does activation of TH1 and TH2 cells induce?
TH1 - Autoimmunity.
TH2 - Allergy
What sort of cytokines are produced by TH1 and TH2 cells respectively?
TH1 - inflammatory cytokines (IL-2 and TNF-alpha).
TH2 - IL-4, IL-5, IL-6 and IL-13
Describe food allergy.
An immune system reaction that occurs soon after eating a certain food. It involves, TH2 immune activation, IgE antibody production, mast cell, eosinophil and basophils accumulation.
Describe food intolerance.
This involves difficulty in digesting certain foods. It is a non-IgE mediated response and doesn’t involve the immune system. Food intolerance may involve IgA antibody production (mucous), Active Treg differentiation and a dampened innnate/adaptive Immunity.
How does lactose cause the symptoms of lactose intolerance?
Lactose accumulation in the bowel increases the osmotic load —> increased water in the lumen —> diarrhoea.
When lactose accumulates in the bowel, colonic bacteria act on it to produce —> Short chain fatty acids and gas —> bloating, flatulence, abdominal pain.
What are the mechanisms of coeliac disease.
Autoantibodies against gliadin (gluten epitomes) and/or transglutaminase.
Define autoimmunity.
When the body’s immune systems attacks the body’s own tissues or organs. It is a misdirected immune response, typically involving an exaggerated (hypersensitive) immune response (TH1 or TH17) to self antigens.
