tolerance and autoimmune diseases Flashcards
T cell tolerance: Positive selection
double positive
Interact with MHC + self = survive
(MHC restriction)
T cell tolerance: Negative selection
Single positive
high affinity with TCR - MHC + self = death
intermediate affinity with MHC + self =survive
AIRE gene
autoimmune regulator gene in the thymus
role in negative selection
Defect in AIRE
results in incomplete deletion of auto reactive T cells
APECED Syndrome
Autoimmune PolyEndocrinopathy Candidiasis Ectodermal Dystrophy syndrome
(polyglandular autoimmune syndrome)
Central Tolerance
Deletion of immature self reacting lymphocytes, receptor editing B cells Negative selection T cells
Peripheral Tolerance Due to:
- Sequestration,
- Treg
- Anergy: Lack of costimulatory signal,
- Too high conc. Of self antigens
peripheral tolerance T regulatory cells
CD4+
CD25+
*** Foxp3+
FoxP3+
master regulator gene
Mutation in FOXP3 gene
IPEX syndrome
IPEX syndrome
• Immune dysregulation
Polyendocrinopathy
Enteropathy
• X linked causes early death
– Watery diarrhea
– Eczematous dermatitis
– Polyendocrinopathy
– Coob’s test +
What causes Breakdown of Immune Tolerance?
Infection: molecular mimicry (cross reactivity)
Mutation in FOXP3, and AIRE genes
Organ-specific
Response is against antigens in localized particular organ
Systemic
gens
Mechanism of tissue injury
Hypersensitivity type II, III, IV