Immune Disorders Flashcards
What is a hypersensitivity reaction?
A reaction due to an exaggerated or inappropriate adaptive immune response to an antigen/immunogen causing tissue damage
How many hypersensitivity reactions are there?
4
What are the 4 types of hypersensitivity reactions?
Immediate (type I) Cytotoxic (type II) Complex mediated (type III) Delayed (type IV)
What is immediate hypersensitivity?
An immediate reaction after contact with an immunogen (allergen)
What is anaphylaxis?
A generalised type I reaction, leading to vasodilation and constriction of bronchial smooth muscle that can result in death
Which antibody mediates type I hypersensitivity?
Ig E
What is an allergen and give examples?
An immunogen that causes an allergy
EG. pollen, animal dander and drugs like penicillin
What are the type of mast cell granules?
Histamine
Eosinophil chemotactic factor
Neutrophil chemotactic factor
What is type II hypersensitivity?
Antibodies are directed against antigens on the surface of specific cells or tissues
What antibodies mediate type II hypersensitivity
Ig M
Ig G
What are the consequences of an antibody binding to an antigen?
Complement activation
What does compliment activation lead to?
Cell lysis
Deposition of complement components (opsonisation)
Macrophage and neutrophil activation
What are some examples of type II hypersensitivity?
Blood transfusion
Hyperacute graft rejection
Haemolytic disease of newborns
Goodpasture’s syndrome
What is haemolytic disease of the newborn?
Rhesus incompatibility
What are the effects of rhesus incompatibility
Spontaneous abortion
Born with mild jaundice or HDN
What is type III hypersensitivity?
Antibodies are directed against soluble antigens in serum
Can also be directed against widely distributed antigen
Deposited antigen-antibody complexes then lead to damage in affect organs
What are some examples of type III hypersensitivity?
Persistent infections where antibodies are formed against microbial agents (Chronic hep B)
Autoimmunity where antibodies formed against self antigens and immune complexes
What are the nature of immune complexes?
Can be precipitates which cause problems locally
Can be soluble, which cause problems mainly in kidney, blood vessels and joints
What is intrinsic allergic alveolitis?
An occupational disease due to inhalation of immunogenic proteins or spores
What are examples of intrinsic allergic alveolitis?
Farmer’s lung
Mushroom worker disease
Coffee worker disease
What is Farmer’s lung?
Mild cough that progresses into emphysema
Sensitisation to spores of thermophilic actinomycetes which grow in damp hay
Years of exposure lead to high levels of Ig G
Immune complexes then precipitate in lungs
How does precipitate in farmers lung cause emphysema?
Complement activates
Initiates inflammation
Destroys alveolar tissue
Fibrosis (tissue repair)
What is the treatment for Farmer’s lung?
Early diagnosis
Avoidance
Corticosteroids
What is serum sickness?
Sickness following treatment of an active infection with antibodies
For example, treating diptheria using serum from a horse immunised against diptheria
How long does it take to develop serum sickness symptoms and what are they?
7 days Weakness Pains Fever Rash Oedema
How long does it take for type IV hypersensitivity reactions to occur?
72 hours to weeks
What is contact hypersensitivity mediated by?
T lymphocytes
Macrophages
What is contact hypersensitivity?
Dermatitis caused by exposure to biological stains, hair dye, poison ivy, nickel salts and mercuric salts (tattoos)
What is the treatment for type IV hypersensitivity?
Avoidance
Corticosteroid creams
Desensitisation
What is sensitisation
Initial contact leading to a cell mediated immune response
What is autoimmunity?
A breakdown of self tolerance
What is self tolerance?
Failure to respond to self antigens
What are two types of self tolerance?
Central tolerance
Peripheral tolerance
What is self tolerance?
Deletion of self reactive T cells
What is peripheral tolerance?
Clonal anergy
Deletion
Active suppression
Presence of autoreactive B cells
What causes the stimulation of self reactive lymphocytes?
Failure to eliminate self reactive lymphocytes
Failure of suppression
Occur after microbial infections
What are the two types of autoimmunity?
Organ specific
Systemic
What is organ specific autoimmunity?
Auto antigen localised to one organ
What factors influence susceptibility to autoimmunity?
Genetics
Environment
Hormonal
What are the two types of immunodeficiency?
Primary
Acquired/secondary
What is primary immunodeficiency?
T cell defect
B cell defect
Phagocytosis defect
Complement defect
What causes secondary immunodeficiency?
Malnutrition
Treatment (X-rays)
Infection (HIV)
