Hypersensitivity and Autoimmune Disease Flashcards
Type I hypersensitivity
- Responsible for immediate hypersensitivity typically to allergens
- Role of IgE in type I hypersensitivity, especially with regard to activating mast cell degranulation
Type II hypersensitivity
- Tissue and cellular targeting by the immune system
- Role of antigen-specific IgG autoantibodies
- Mechanisms of damage induction
- Inflammatory and non-inflammatory mechanisms
- Examples
Type III hypersensitivity
- Tissues targeted by type III hypersensitivity responses
- Immune complex mediated damage – spontaneity of lesion appearance
- Examples
Atopy =
predisposition to allergy
Autoimmune disease =
failure or breakdown of immune system that maintains tolerance to self tissues.
Loss of tolerance in autoimmune disease is probably due to
abnormal selection or lack of control of self-reactive lymphocytes (B and T-cells).
Damage in different autoimmune diseases may result from different effector mechanisms
Autoimmune disease is treated through
- Blanket immunosuppression
- Side-effects including infection
- Targeted selective approach – target the aberrant immune activation while leaving the rest of the immune system intact
Autoimmune disease: the cost to individuals and society
- Estimated that 1 in 20 individuals in the western world suffer an autoimmune syndrome
- Typically chronic long-term disorders [low mortality but high morbidity]
- Treatments limited to dealing with the symptoms rather than curing the disease
- Treatments e.g., steroids carry their own risks
- Patients require intense, careful management and treatment costs run into billions worldwide
Type I hypersensitivity steps
- Exposure to allergen occurs in the mucosal lining
- Activation of THF stimulation of IgE class switching in B cells.
- Production of IgE
- Binding of IgE to FCERI on mast cells
- Repeated exposure to allergen
- Activation of mast cell causes release of mediators
What causes autoimmune disease?
No known aetiological agents
Hypersensitivity responses
- Hyper response from the immune system
- Harmful immune responses that may produce tissue injury and cause serious disease
- 4 categories: Type I, II, III, IV (V)
antibody mediated hypersensitivity include
Type I, II (V), and III
T cell mediated hypersensitivity include
type IV
Autoimmune diseases usually fall into hypersensitivity
Type II, III, and IV categories depending on the type of damage associated with the disease.
mediators of type I hypersensitivity and types
Vasoactive amines, lipid mediators (histamine)
- targets vascular/smooth muscle - immediate hypersensitivity reaction (minutes after repeat exposure to allergens)
Cytokines
- causes inflammation - late phase reaction (2-4 hours after repeat exposure to allergens)
type 1 hypersensitivity can cause
Vasodilation
Vascular leak
Broncho-constriction
Inflammation
mediators of type I hypersensitivity and types
Vasoactive amines, lipid mediators (histamine)
- targets vascular/smooth muscle - immediate hypersensitivity reaction (minutes after repeat exposure to allergens) - IgE mediated effects
Cytokines
- causes inflammation - late phase reaction (2-4 hours after repeat exposure to allergens)
type 1 hypersensitivity can cause
Immediate reaction
- Vasodilation, - Oedema - Vascular congestion
Late reaction
- Eosinophil - Neutrophil - T cell infiltrates
type 1 hypersensitivity occurs when
IgE attaches to soluble antigen and causes an allergic reaction
type 2 hypersensitivity occurs when
IgG attaches to the cell or matrix antigen and causes:
- AIHA
- ATP
- Rheumatic fever