Autoimmunity

This is due to either a deficit in central or peripheral tolerance and the cause is usually genetic. It is characterized as type II hypersensitivity reaction and normally presents at a young age.  

Central Tolerance

• Thymocytes and medullary epithelial cells in thymus cannot present TRAs so no negative selection
• Lack of AIRE gene leads to APECED
• Symptoms: allopecia, diabetes, graves disease, addisons disease
• 

Peripheral Tolerance

• Lack of regulatory T-cells: cannot induce apoptosis in self-T-cellactivated  in without costimulation
• Lack of foxp3 gene leads to IPEX
• Symptoms: allopecia, diabetes, graves disease, addisons disease, IBS

This is due to either a deficit in central or peripheral tolerance and the cause is usually genetic. It is characterized as type II hypersensitivity reaction and normally presents at a young age.  

Central Tolerance

• Thymocytes and medullary epithelial cells in thymus cannot present TRAs so no negative selection
• Lack of AIRE gene leads to APECED
• Symptoms: allopecia, diabetes, graves disease, addisons disease
• 

Peripheral Tolerance

• Lack of regulatory T-cells: cannot induce apoptosis in self-T-cellactivated  in without costimulation
• Lack of foxp3 gene leads to IPEX, X-linked so only affects males
• Symptoms: allopecia, diabetes, graves disease, addisons disease, IBS

Genetic defect in component of immune system, X-linked in 70% of cases, presents in the young.

Cellular

• Chronic granulomatous disease (neutrophils lack cytochrome b and hydrogen peroxide)
• SCID (adenose deaminase deficiency essential for lymphocyte production)
• X-SCID (IL-2RG encodes y-chain for cytokine receptors so T-cells not activated)
• Leukocyte adhesion defect (lack of adhesion molecules so struggle to enter tissue)

Lymphoid

• Di Georges Syndrome (no thymus due to lack of CATCH22 gene therefore no mature T-cells)

Soluble Mediator

• Bare lymphocyte Syndrome: No MHCII, Agammaglobulinaemia (no Ig), IgA deficiency
• Complement deficiency or Cytokine deficiency
• TLR, MBL defects alter innate immunity along with CAM defects