Lecture 11- Overview of classification of immunological disease Flashcards
why are the immunological disease a result of?
Immune system may fail to control the infection:
Pathogen factors-Evasion mechanism
Host factors- immunodeficiency
How can the immune system may cause disease directly?
- Failure of tolerance- allergy and auto-immunity
- immune system inappropriately activated for unknown reason- IBD
what are the type 1 hypersensitivity according to gel and coombes?
- IgE mediated allergy
- B cells class switch to IgE antibody. Secreted IgE is picked up by tissue mast cells and circulating basophils
- Cross-linking of allergen-specific IgE antibodies by allergen activates the mast cell
- Mast cell rapidly ‘degranulates’ releasing histamine, tryptase and other pre-formed mediators
- Pharmacological effects of histamine lead to symptoms in the affected organ(s)
-In health, believed to assist with parasite immunity
Explain type II hypersensitivity?
- Refers to pathology directly mediated by antibodies
- mismatch blood transfusion reactions are an example of type II hypersensitivity
- IgM antibodies against AB antigens develop during first year of life
- The antibodies are an example of isoantibodies – develop against similar antigens on surface of gut bacteria and cross-react with red cell antigens
Describe Type 2 hypersensitivity: haemolytic disease of newborn?
- Major blood group system is ABO
- D antigen (rhesus) is a secondary classification
- Majority of the population are D+
- Mother may be sensitised by exposure to the fetal red cells during pregnancy
- Parturition
- Trauma
- Antibodies may cause disease
Describe type 2 hypersensitivity auto-immune haemolysis?
- Red blood cells plus anti-RBC autoantibodies EITHER
- FcR cells in fixed mononuclear phagocytic system
- Phagocytosis and RBC destruction
- Complement activation and intravascular haemolysis
- Lysis and RBC destruction
Haemolytic disease of the newborn and complications?
- Autoimmune haemolysis highly deleterious to fetus
- growth retardation, cardiovascular failure, neurotoxicity from high bilrubin
Haemolytic disease of the newborn and management?
- Rhesus-negative mothers with rhesus+ partner are given anti-D IgG during pregnancy
- At 28 weeks routinely
- After accidents, miscarriage or surgical delivery
- Binds to fetal red cells entering circulation; fetal red cells then destroyed, preventing sensitisation
describe Type III hypersensitivity?
- Describes the disease caused by the complex of antibody and antigen complex
- normally these are soluble and are removed by the spleen
- in some situation they become insoluble
What are the possible situation when the antibody and antigen complexes become insoluble?
1) Large quantity of antigen
2) Large quantity of antibody
3) interaction between these two are very strong
- complexes are of the correct size
describe the features of the local immune complex disease?
- painful lesions of the fingertip pulps due to deposition of the circulating immune complexes
- May be seen in infective endocarditis
- may be seen in other diseases with immune complex deposition SLE
Explain :Type III hypersensitivity: Serum sickness causes?
A generalised transient immune complex mediated syndrome
-Mainly results from injection of certain immunogenic drugs or anti-sera produced in animals- e.g. snake evenomation
What are the symptoms of the Type III hypersensitivity: serum sickness?
- Rash
- Fever
- Arthritis
- Glomerulonephritis
Describe the Type III hypersensitivity: Hypersensitivity pneumonitis?
AKA- extrinsic allergic alveolitis
- Patient becomes sensitised to an environmental antigen by repeated exposure, producing large quantities of IgG antibodies
- Immune complexes form in the lung upon re-exposure causing shortness of breath and cough
Describe the Type III hypersensitivity: Hypersensitivity pneumonitis causes?
mould spores in hay (farmers)
Pigeon feathers and stool (pigeon fanciers lung)
-Initially transient- repeated exposure causes lung scarring
