Regulation Of Lymphocytes Flashcards
What is a linear epitope?
Amino acid sequence held by MHC and recognise by TCR
There are 3 types of autoimmune response. List the 3 with an example of each:
- disease is chronic due to self antigens eg Crohn’s disease where gut bacteria is destroyed
- allergy mediated by IgE and mast cells
- immune response is too large: hyper cytokinemia and sepsis.
Triggered by pathogens entering wrong compartment (sepsis)
Big systemic immune response - shuts body down (fever)
Broad Dysfunction of immune response
What are 3 signals to license a response?
- antigen recognition
- Co stimulation (other cells interact) T cell receptors come together for signalling to work. Spatial recognition.
- Cytokine release - cell signalling
Describe the 3 phases of cell mediated immunity:
- induction: dendritic cells activates T cell
- Resolution - no tissue damage. Debris removed by macrophages
- Repair - scar tissue. Fibroblasts and collagen synthesis
Response against pathogens decline as infection eliminated
- apoptosis of lymphocytes that lost their survival signals
- Memory cells are the survivors
Active control mechanisms limit responses to PERSISTENT antigens (self, chronic infection, tumours). Give me some examples of this:
- cells turn themselves off
- If T cell sees antigen for too long, markers on surface become repressive (Cancer immunotherapy, remove the repressive markers.)
What is Immunological tolerance?
specific unresponsiveness to an antigen that is induced by exposure of lymphoecytes to that antigen. (Lymphocyte is unresponsive)
What is central tolerance?
destroying self reactive t/b cells before they enter circulation
How does central tolerance work?
- immature B cell in bone marrow.BCR gene shuffles. If receptor sees self antigen eg in bone marrow - apoptosis
- T cell need to recognise self MHC and antigen complex. Too weak too strong binding causes apoptosis.
How does the AIRE (autoimmune regulator) gene promote self tolerance?
it allows thymic expression of genes from other tissues.
Mutations in AIRE cause multi organ autoimmunity
What is Peripheral tolerance?
destroy self reactive t/b cells in circulation
Explain 3 mechanisms of peripheral tolerance:
- ANERGY: when a naive t cell sees its MHC ligand lacking the costimulatory proteins, it becomes anergic (tolerised less likely to be stimulated in future) not activated
- IGNORANCE: certain areas, antigen too low to trigger T response, or not enough T cells eg eyes and brain (immunogically privelieged)
- ANTIGEN INDUCED CELL DEATH: sees the antigen, becomes killed
