Week 5- Immune Tolerance Flashcards
What is immune regulation?
Control of the immune system to prevent inappropriate responses against pathogens or self cells
What does immune regulation help avoid?
Tissue damage, excessive lymphocyte activation
What arises if there is failure in immune regulation?
Inflammatory disease
What are the 3 main problems that arise due to failure of immune regulation?
Autoimmunity, allergy, hypercytokinemia/sepsis
What is autoimmunity and how can it arise?
Immune response against a self antigen, can be systemic or organ specific, occurs due to genetic susceptibility or environmental triggers
What is allergy?
Immune response against a non infectious agent that can cause tissue damage or disease
What are the 2 ways allergies are mediated? Give an example for each
- Antibodies and mast cells: acute anaphylactic shock
2. T cells: delayed type hypersensitivity
What is hypercytokinemia?
A very excessive immune response eg fever
What is sepsis?
Pathogens entering the wrong body compartment
NOTE sepsis is not just blood infection, this is known as septicaemia
What are the 3 stages required to cause an immune response?
- Antigen recognition
- Co stimulation
- Cytokine production
What is an immune synapse?
An area cleared to allow many T cells to come together and communicate
What are the 3 phases of cell mediated immunity?
- Induction: foreign antigen recognized, components displayed on MHC and T cell involvement starts
- Effector: T cell is activated and proliferates
- Memory: Pool of T cells is reduced to some are kept as memory
What are the 3 outcomes of an immune response?
- Resolution: everything returns to normal with no tissue damage
- Repair: healing with scar tissue formation (fibroblasts and collagen synthesized)
- Chronic inflammation: ongoing persistent attempts to repair damage
What is central tolerance? How do B and T cells undergo it?
When self B/T cells are destroyed before they enter circulation.
For B cells, if in the bone marrow they encounter an antigen that can cross link their IgM they undergo apoptosis
For T cells if it doesn’t bind to MHC or binds to self MHC strongly, they undergo apoptosis
What is peripheral tolerance?
When self B/T cells are destroyed in circulation
What is AIRE?
A specialized transcription factor that allows thymic expression of proteins from the whole genome so that T cells can see many diff proteins
What are the 3 states T cells can be in?
- Anergy: T cells need co stimulation to be activated but when they see MHC with without co stimulatory protein they enter a state of anergy/shut down
- Ignorance: there may be costimulation but not enough to induce a T cell response
- Antigen induced cell death: when there is no co stimulation and the T cell is killed
What are the subtypes of T helper (CD4) cells?
Th1/2/17, Tfh, Treg
What does Th1 do?
It produces interferon gamma which boosts intracellular responses
What does Th2 do?
Produces IL 3/4/5 which boosts the multicellular response
What does Tfh do?
Follicular helper, it produces IL 21 which allows generation of isotope switched antibodies
What does Th17 do?
Helps fight bacteria by producing IL17
What does Treg do?
Controls the immune response, inhibits other T cells, helps produce IL10 which shuts down the immune response
What is cross regulation?
The phenomenon wherein if one type of T cell is produced, it inhibits other types of T cell to refine the immune response and increase effectiveness
