Tolerance and Autoimmunity Flashcards
4 criteria for an autoimmune disease?
Evidence of disease specific adaptive immune response in the affected target tissue/organ/blood
Passive transfer of auto reactive cells or antibodies replaces the disease
elimination of the autoimmune response eliminates the disease
history of autoimmune disease/MHC associations
factors for autoimmune disease? (6)
Microbiome Stress Diet Sex Infections Genes
effector mechanism of autoimmunity resembles which HS reactions?
mechanisms resemble those of hypersensitivity reactions, types II, III, and IV
What is the hygiene hypothesis? What evidence supports this?
that if the immune system isn’t fighting infection it may begin to fight self
- Incidence of autoimmune disease (and hypersensitivity) is increasing
During pregnancy what happens to autoimmune diseases and why?
- During pregnancy there is a shift away from inflammatory responses to help protect the fetus, so often diseases go away during pregnancy then come back (e.g. arthritis)
Some important autoimmune diseases? (5)
RA T1DM MS SLE Autoimmune thyroid disease
Example of a specific target autoimmune disease? (3)
Graves’
T1DM
Pernicious anaemia
Example of a nonspecific target autoimmune disease? (3)
SLE/RA/Vasculitis
What is a t2 HS reaction
- Antibody response to cell surface or insoluble extracellular matrix antigen (against insuluble antigen
What is a t3 HS reaction
- Immune complex formed by antibody against soluble antigen that go into circulation
What is a t4 HS reaction
- T-cell mediated disease (Delayed type hypersensitivity reaction,
What is Goodpastures syndrome
antibody binds to basement membranes in kidney- leads to complement activation and inflammation
Summarise Graves disease
antibodies against TSH receptor cause release of thyroid hormone w/o negative feedback
Example of a T3 HS disease
SLE
3 examples of T4 HS diseases?
Insulin dependent diabetes mellitus
RA
MS
Autoantigen and pathology and HS reaction type of:
RA
T4
unknown synovial joint antigen
Joint inflammation and destruction
Autoantigen and pathology and HS reaction type of:
MS
Myelin basic protein, proteolipid protein
T4
Brain degeneration (demyelination) weakness and paralysis
What do CD8+ cells recognise
MHC Class I
What do CD4+ cells recognise
MHC Class II
What is the dominant genetic factor affecting susceptibility to autoimmune disease?
MHC class II
What is tolerance defined as
ACQUIRED INABILITY TO RESPOND TO AN ANTIGENIC STIMULUS
2 types of tolerance?
Central and peripheral
What is central tolerance?
The elimination of self-reactive lymphocytes during lymphocyte development
What is peripheral tolerance
Anergy, active suppression (by regulatory T cells), ignorance of antigen (non-exposure/ignorance to antigen)
Where does central tolerance occur (2)
THYMIC EPITHELIAL CELLS (TECs) and DENDRITIC CELLS (DCs)
What 3 categories does the thymus separate lymphocytes into
- Useless (can’t see MHC) die by apoptosis
- Useful (see MHC weakly) receive signal to survive- “Positive selection”
- Dangerous (see self strongly) receive signal to die by apoptosis- “Negative selection”
What % of thymocytes survive thymus selection
5
Which type of immune cell goes to the thymus
pre T-cells
Which type of immune cell matures in the bone marrow
B cells
What happens to a B cell that has no self reaction in the bone marrow
Migrates to periphery and matures
What happens to a B cell that has a reaction to a multivalent self molecule in the bone marrow
Clonal deletion or receptor editing leading to apoptosis
What happens to a B cell that has a reaction to a soluble self molecule in the bone marrow
Migrates to periphery and becomes anergic
What happens to a B cell that has a reaction to a low-affinity-non-crosslinking self molecule in the bone marrow
Migrates to periphery and becomes a mature clonal ignorant B cell
What is apeced and what does it effect? (6)
- APECED is a rare autoimmune disease which affects the endocrine glands: Thyroid Kidneys Chronic mucocutaneous candidiasis Gonadal failure DM Pernicious anaemia
What does failure of central tolerance result in
- APECED
What causes Apeced
mutations in the transcription factor AIRE (autoimmune regulator) gene
What is AIRE important in
- AIRE is important for the expression of ‘tissue-specific’ genes in the thymus
Many of the genes that are implicated in genetic susceptibility to autoimmune diseases are involved in… (3)
- induction of tolerance
- apoptosis
- clearance of antigen
3 mechanisms for inducing and maintaining tolerance in the periphery?
- Anergy
- Suppression by regulatory T cells
- (Ignorance of antigen)
What do naive T cells need for full activation? Examples of what they need? (3)
co-stimulation for full activation: CD80, CD86 and CD40 are examples of costimulatory molecules expressed on APC
What does stimulation without a co-stimulatory molecule lead to
Anergy
How does anergy occur
stimulation without a co-stimulatory molecule lead to
When does immunological ignorance occur (2)
when antigen concentration is too low in the periphery
and when relevant antigen presenting molecule is absent:
Which MHC class are most cells in the periphery
class I
Where does immunological ignorance occur (3)
immunologically privileged sites such as eye, testes and PNS
Why might cells at immunologically privileged sites react against autoantigens
They have never been tolerised
What transcription factor is required for Treg development
FOX P3
FOXP3 is required for what
Treg development
IPEX stands for what
Immune dysregulation, Polyendocrinopathy, Enteropathy and X-linked inheritance syndrome
Symptoms of IPEX? (5)
- Early onset insulin dependent diabetes mellitus
- Severe enteropathy
- Eczema
- Variable autoimmune phenomena
- Severe infections
Symptoms of IPEX? (5)
- Early onset insulin dependent diabetes mellitus
- Severe enteropathy
- Eczema
- Variable autoimmune phenomena
- Severe infections
Ways in which infections can cause autoimmunity? (5)
- Infections may carry out molecular mimicry of self-molecules
- Induce changes in the expression and recognition of self-proteins
- Induction of co-stimulatory molecules or inappropriate MHC class II expression: pro-inflammatory environment
- Failure in regulation by effecting/infecting regulatory T-cells
- Immune deviation shift in type of immune response e.g. Th1-Th2
- Tissue damage at immunologically privileged sites