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Clinical Pathology G > Allergy > Flashcards

Flashcards in Allergy Deck (23):
1

What is allergy and hypersensitivity?

Undesirable, damaging, discomfort-producing and sometimes fatal reactions produced by the normal immune system (directed against innocuous antigens) in a pre-sensitized (immune) host.

2

What are the two immunopathological classifications?

Coombs & Gell 1963- IV types
Extended classification- type V

3

What is the immunopathogenesis of type ii cytotoxic reactions?

IgG/IgM Ab response against combined self/foreign antigen at the cell surface- complement activation/phagocytosis/ADCC

4

What are the clinical features of type ii cytotoxic reactions?

Onset minutes to hours
Cell lysis and necrosis

5

What are the common antigens of type ii cytotoxic reactions?

Penicillin

6

What are the associated diseases of type ii cytotoxic reactions?

Erythroblastosis fetalis,
Goodpasture's nephritis

7

What is the immunopathology of type iii immune complex?

IgG/IgM Ab against soluble antigen- immune complex deposition

8

What are the clinical features of type iii immune complex?

Onset 3-8h
Vasculitis

9

What are the associated diseases of type iii immune complex?

SLE

10

What is the traditional cause of type iii immune complex?

serum sickness

11

What is the immunopathology of type IV delayed hypersensitivity?

Antigen specific T-cell mediated cytotoxicity

12

What are the clinical features of type IV delayed hypersensitivity?

Delayed onset 48-72h
Erythema induration

13

What is the common antigen of type IV delayed hypersensitivity?

Metals-e.g nickel
(tuberculin reaction)

14

What is the associated disease of type IV delayed hypersensitivity?

Contact dermatitis

15

Why do we get allergies?

Those components of the immune system involved in responses to parasitic infection are also involved in allergic responses

The system has developed to produce a rapid tissue-based response to re-infection

The lack of infectious drive (fewer infections) is a contributory factor in allergic disease

16

What is the immune response to parasitic disease?

Increased levels of IgE
- Total
- Specific to pathogen – cross-reactive
Tissue inflammation with:
- eosinophilia & mastocytosis
- Basophil infiltration
Presence of CD4+ T cells secreting:
- IL4, IL5 & IL13

17

What is the hygiene hypothesis?

Stimulation by microbes is protective

18

What are the genetic influences on the allergic immune response?

Polygenic diseases
Cytokine gene cluster IL3,5,9,13
IL12R; IL4R
FcεRI
IFNγ; TNF

19

Are genetic influences sufficient for disease?

NOT sufficient for disease
ONLY susceptibility

20

What are allergens?

Antigens that initiate an IgE-mediated response
First encounter results in innate & IgM response

21

What happens in a conventional immune response?

Allergen requires processing
Presentation to T cells & cytokine release
Results in delineation of T-helper subsets into different types

22

What is the immunopathogenesis of an IgE mediated allergic response?

IgE Ab mediated mast cell and basophil degranulation- release of preformed and de novo synthesized inflammatory mediators

23

What are the clinical features of an IgE mediated allergic response?

Fast onset (15-30 min)
Wheal and flare