Gell and Coombs' Hypersensitivity Flashcards
what is a type 1 HSR?
antigen reacts with IgE bound to mast cells
e.g. anaphylaxis, atopy (eczema, asthma, hayfever)
what is a type 2 HSR?
IgG or IgM binds to antigen on cell surface
e.g. AIHA, goodpasture’s, pernicious anaemia, rheumatic fever, pemphigus vulgaris/bullous pemphigoid, acute haemolytic transfusion rxr, immune thrombocytopaenic purpura
what is a type 3 HSR?
free antigen and antibody (IgG, IgA) combine
e.g. serum sickness, SLE, post-strep glomerulonephritis, extrinsic allergic alveolitis
what is a type 4 HSR?
t-cell mediated
e.g. TB, GVHD, allergic contact dermatitis, scabies, guillain-barre, MS, extrinsic allergic alveolitis (chronic phase)
what is a type 5 HSR?
ab recognise and bind to cell surface receptors, either stimulating them or blocking ligand binding
e.g. graves’, myasthenia gravis
what are the five HSRs per the G-C classification?
type 1 - anaphylactic
type 2 - cell bound
type 3 - immune complex
type 4 - delayed hypersensitivity
type 5
what type of HSR is SLE?
type 3 - ag-ab complexes
sle pathogenesis:
1. cellular remnants with nuclear material transferred to lymphatic tissue
2. presented to t cells
3. t cells stimulate b cells to produce IgG auto-ab
4. auto-ab primed to attack DNA/nuclear material
5. results in ag-ab complexes
features of an anaphylactic rxn?
oedema
itchy rash (‘urticarial’)
expiratory wheeze
low blood pressure
what diseases are a/w hla-b51?
behcet’s
what diseases are a/w hla-dq2?
coeliac disease
what diseases are a/w hla-dr3?
addison’s
sle
t1dm
grave’s
mg
what diseases are a/w hla-dr4?
t1dm
rheumatoid arthritis (esp drb1*04:01 and *04:04)
what diseases are a/w hla-a3?
haemochromatosis
what diseases are a/w hla-b27?
ankylosing spondylitis
reactive arthritis
acute anterior uveitis
what diseases are a/w hla-dq8?
coeliac disease
