Hypersensitivity Autoimmunity Flashcards Preview

ME2308 Principles of Disease > Hypersensitivity Autoimmunity > Flashcards

Flashcards in Hypersensitivity Autoimmunity Deck (18)
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  • A group of disorders where the normally beneficial components of the immune response act in an exaggerated or inappropriate fashion to environmental antigens which do not normally cause tissue damage.
  • The exaggerated response, rather than the antigen itself is responsible for the tissue damage which results (bystander damage). 



  • A genetic tendency to produce IgE to normally innocuous, common environmental allergens
  •   (40% of population)



  •   A clinical expression of the atopic tendency
  •   (15-20% of population)


Factors that affect hypersenitivity

  1. Genetics
  2. Environment e.g Allergin
  3. Immune dysregulation
  4. Internal influences



  •  This is where the body recognises an environmental antigen as a pathogen and releases IgE and triggers Mast cell responses.
  • During sensitisation, the allergen is shown to a T helper cell by an antigen presenting cell. This causes B cells to differentiate to produce IgE against the antigen.
  • From then onwards, exposure to the antigen will cause the release of cytokines from Mast cells, resulting in an allergic response.
  • Immediate type hypersensitivity

Things involved:

  • Allergens/allergy
  • IgE
  • Th2 cells 
  • Mast cells
  • Granule associated inflammatory mediators
  • Newly-made inflammatory mediators
  • Atopy► ( genetic tendency to develop allergic diseases e.g asthma)



  • In this type, the body’s antibodies bind to the antigens on its own cell surfaces.
  • Antibodies are produced in response to the antigens on the cell surfaces e.g. when penicillin binds to blood cells
  • IgG and IgM antibodies trigger the complement system causing cell lysis

Things involved:

  • Antibodies
  • Complement
  • Fc receptors
  • ADCC (antibody‐dependent cell‐mediated cytotoxicity)


                                        Type III

  • This form of hypersensitivity is characterised by the formation of immune complexes (clumps of antibodies that have stuck together)
  •  A low conc. of antibody coupled with a large conc. of antigen causes small complexes to form

Things involved:

  • Anitgen-antibodies formation
  • Local arthus
  • Systemic serum sickness reactions


                                                Type IV

  •  The body’s CD4 helper T cells recognise the foreign antigen, and starts to produce cytokines which leads to an inflammatory response.
  • Delayed type hypersensitivity

Things involved:

  • Haptens (binds to proteins to make antibodies)
  • Carrier proteins
  • Th1 cells
  • Antigen-presenting cells
  • Monocytes/macrophage
  • Granuloma formation


 Explain the pathophysiology of early and late phase reactions ►

o   Early Phase Response

  • Occurs within minutes
  •  Preformed mast cell mediators( histamine, heparin, chemotactic factors, tryptase, chymase, eosinophil/neutrophil )

o   Late Phase Response

  •  Newly synthesised mediators (Prostaglandins, leukotrienes)
  •  Th2 cytokines
  •   Eosinophil mediators


 Define the pathophysiology of immune complex formation in localised and systemic Type III Hypersensitivity?

o   Localised

  •   Causes localised inflammation and can be cleared away by macrophages

o   Systemic

  • Complexes are deposited in tissues and organs  such as the skin, joints kidneys and blood vessels


               Define the term autoimmune disease

A large group of clinical disorders characterised by tissue or organ damage mediated by incorrect immune mechanisms targeted at self-antigens.


    Illustrate the factors involved in the aetiology of autoimmune disease►

Caused by an interaction of

o   Genetic Factors

o   Immune Regulatory Factors

o   Hormonal Factors

o   Environmental Factors



 Describe the pathogenic mechanisms involved in autoimmune disease►

o   Cell-mediated

o   Antibody-mediated

o   Antibody + Complement

o   Immune Complex-mediated

o   Recruitment of innate compunds


   List the organ specific autoimmune disease►

1. Thyroid

·       Hashimoto’s Thyroiditis

·       Primary Myxoedema

·       Thyrotoxicosis

2. Stomach

·       Pernicious Anaemia

3. Adrenal

·       Addison’s Disease


List the non-organ specific autoimmune disease.►

·  Dermatomyositis - Skin

·   Scleroderma- kidneys

·   SLE (Systemic Lupus Erythematosus )- Joints

·    Rheumatoid Arthritis


Immunity pic


Immune complex formation►

1) Normal / physiological: Protective mechanisms:

  - opsonisation

  - transportation

  - destruction

2) Pathological

  - antigen factors

  - host response factors

  (skin, joints, kidney, blood vessels)


Immunological tolerance►


  • +ve / -ve selection


        -T regulatory cells

        - antibody idiotype regulation

        - immune complex formation

        - oral tolerance

        - Th17 cells