Hypersensitivity and autoimmunity Flashcards
What is an autoimmune disease?
A failure or break down of the immune system which maintains tolerance to self tissues
Provide examples of different ways to treat autoimmune disease
Blanket immunosuppression(can lead to infection) Target selective approach9target the aberrant immune activation whilst leaving the rest of the immune system intact)
Define hypersensitivity
Hyper response from immune system
How many types of hypersensitivity are there?
4
Describe type 1 hypersensitivity
- IgE
- Soluble antigen(allergen)
- Allergy
(• 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 APC. 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. )
Describe type 2 hypersensitivity
- IgG
- Cell or matrix antigen
- AIHA or rhematic fever
(• 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)
Describe type 3 sensitivity
-IgG
-Soluble antigen
-SLE
-Arthritis
(• 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)
Describe type 4 sensitivity
- Th1, Th2, CTL
- soluble antigen, cell
- antigen,inf-gamma
Type 1 diabetes
(• The body’s CD4 helper T cells recognise the foreign antigen, and starts to produce cytokines which leads to an inflammatory response. )
Describe central tolerance
The process of eliminating lymphocytes that are self reactive
Describe peripheral tolerance
The process of eliminating T cells which avoided central tolerance
What type of lymphocytes acquire peripheral tolerance?
Mature lymphocytes in the peripheral tissue
What type of lymphocytes acquire central tolerance
Immature lymphocytes during their development
How may self reactive lymphocytes escape negative selection?
due to low affinity to self MHC/antigen and the exclusive expression of some proteins in the periphery
Name some factors which affect auto-immune diseases?
genetic predispositions
Hormonal/sex
Environmental co-factors
immunity regulatory factors
Describe systemic autoimunne disease
Systemic
Autoimmune process is spread throughout the body - affects more than one organ. eg systemic lupus erythematosus (SLE)