Week 12 - Autoimmunity and Tolerance Flashcards
Natural Autoimmunity (Good autoimmunity)
B1 cells (CD5+) produce polyreactive, low affinity binder IgM natural autoantibodies that recognize conserved molecules.
Heat Shock Proteins, Enzymes (CyteC), Membrane Proteins (Beta2m), Cytoplasmic Proteins (Actin), DNA, IL1, Albumin, IgG.
These are all examples for shared ______ of Human and Microbes that are possibly recognized by _______ ________.
These are all examples for shared Antigens of Human and Microbes that are possibly recognized by Natural Autoimmunity.
Natural Autoimmunity is apart of the process of the development of ______ since over time the reaction gets less and less _______ with the exposure.
Natural Autoimmunity is apart of the process of the development of Tolerance since over time the reaction gets less and less powerful with the exposure.
Pathological autoimmunity develops if the
immune _______ is broken or insufficient.
Pathological autoimmunity develops if the
immune tolerance is broken or insufficient.
Immune tolerance which is unresponsiveness to a given antigen could be either :
Peripheral or Central
T cells that recognize self peptide MHC
complexes with high avidity, undergo
clonal deletion (apoptosis) in a process called _______ ______ this is part of the ______ _________
T cells that recognize self peptide MHC
complexes with high avidity, undergo
clonal deletion (apoptosis) in a process called Negative Selection this is part of the Central Tolerance.
In Negative Selection, T cells with weak or intermediate TCR avidity get to the ________ .
In Negative Selection, T cells with weak or intermediate TCR avidity get to the periphery.
Peripheral tolerance mechanisms:
Anergy
Inability to respond to stimuli in the absence of costimulation
Peripheral tolerance mechanisms:
Ignorance
low avidity TCR binding
Peripheral tolerance mechanisms:
Antigen Segregation - Immunoprivileged sites
Brain, Testis, Thyroid, Pregnant Uterus (In general no Lymphatic drainage)
For example BBB is the segregating entity of the Brain
Peripheral tolerance mechanisms:
Antigen Segregation - Molecules Involved in its sites
- Immunosuppressive cytokines e.g. TGF-Beta , IL 10
- FasL expressed by Cells allow for Avoidance from T cell
Release of hidden (cryptic) antigens from immune privileged sites - Give an example and What could be the consequence.
Injury of the eye causes the release of its protein antigens to the Blood and eventually lymphatic system.
Possible attack on Eye tissues by T cells can happen.
Peripheral tolerance mechanisms:
Cytokine Devations, by Helminths Response, Allergy or cell mediated Immune response could (3 Examples) -
Damage immune tolerance and lead to:
Rheumatoid Arthritis, Crohn’s or Multiple Sclerosis
Peripheral tolerance mechanisms:
Regulatory T cells - CTLA4
Aka CD152 , is a protein receptor that acts as an “off” switch when bound to CD80 or CD86 on the surface of antigen-presenting cells.
Peripheral tolerance mechanisms:
Regulatory T cells - PD-1
Programed Cell Death Protein-1 (CD279) - Promotes apoptosis in antigen-specific T-cells in lymph nodes and reduces apoptosis in regulatory T cells.
Peripheral tolerance mechanisms:
Regulatory T cells and TH3 cells- FOX3P
Master regulator transcription factor upregulating regulatory T-cell function, and may inhibit transcription of key genes following stimulation of T cell receptors.
Peripheral tolerance mechanisms:
Regulatory T cells - Cytokines Released
IL-10 and TGF-beta (immunosuppressive)
Peripheral tolerance mechanisms:
TH3 cells - Cytokines Released
IL-10 and TGF-beta (immunosuppressive)
Peripheral tolerance mechanisms:
Tr1 cells - Cytokines Released
IL 10 (immunosuppressive)
Peripheral tolerance mechanisms:
Clonal exhaustion
Activation induced T cell death (AICD),
apoptosis is mediated by Fas FasL interaction.
Autoimmune diseases - 6 General Principles for all of them
MB5UFC
- Multifactorial: Polygenic +Environmental factors
- B cell , T cell , immune complex mediated
- 5% of the adult population
- Usually in adulthood
- Frequent in women
- Characterized by Exacerbations and Remissions
Genes determining autoimmune disease susceptibility
MHC, AIRE, FAS, PD, CTLA4, Inhibitory Fc receptors
Cross reactivity (molecular mimicri)
Viral and bacterial peptides might mimic self peptides causing Autoimmunity
Bacterial Example for Molecular Mimicry
Streptococcal antigens → similar to endocardial antigens → inflammation , valve deformity → Rheumatic fever.
Viral Examples for Molecular Mimicry:
Poliovirus - Protein in virus and What is mimicked
Poliovirus
VP2 - ACh receptor
Viral Examples for Molecular Mimicry:
HIV - Protein in virus and What is mimicked
HIV
p24 - IgG Constant Region
Viral Examples for Molecular Mimicry:
Measles - Protein in virus and What is mimicked
Measles
p3 - Myelin Basic Protein
__________ (e.g. bacterial toxins) bind the MHC II molecules and the T cell receptors from the outside, thus, a high number of T cell clones can be activated in a ___ _______ way.
Superantigens (e.g. bacterial toxins) bind the MHC II molecules and the T cell receptors from the outside, thus, a high number of T cell clones can be activated in a non specific way.
Autoimmune Diseases Associated with Brain: (3 examples)
Multiple Sclerosis
Guillain Barre Syndrome
Autism