Hypersensitivity and Autoimmunity Flashcards Preview

Yr1 -S1 - Principles of Disease > Hypersensitivity and Autoimmunity > Flashcards

Flashcards in Hypersensitivity and Autoimmunity Deck (35):
1

hypersensitivity

a group of disorders in which the normally beneficial components of the immune response act in an exaggerated or inappropriate fashion to environmental antigens

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Types I, II , III are mediated by

antibodies

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Types IV is mediated by

the inappropriate actions of Th1 cells

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Type 1 hypersensitivity also called

allergy

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Type 1 hypersensitivity principally arises through...

inappropriate synthesis of IgE by the immune system

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Environmental antigens can be

Airbourne
ingested
injected
skin contact

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allergic problems can arise through a combination of

genetic factors
environmental factors
hormonal and neurological influences
immune regulatory factors

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Mere synthesis of IgE on its own is not enough to produce...

clinical allergy

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IgE associated with symptom

Allergy

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IgE associated with NO symptoms

atopy


a state of sub-clinical immune sensitisation

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what portion of the population are atopic?

40-50%


(but only half of this have any clinical problems arising)

12

allergy is the end result of

complex interplay of a number of factors

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Allergen exposure --> mast cell -->

allergen specific IgE -->


release of inflammatory mediators

14

Type II is mediated by

IgM or IgG antibodies

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IgM or IgG directed at

antigens on the surface of the cell or fixed within certain tissues

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In type II - once the antibody has bound to the relevant antigen - damage to tissue arises through

complement activation

Fc binding of immunoglobulin and stimulation of phagocytes

ADCC

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Type III arises from abnormal

deposition of formed antigen / antibody complexes (immune complexes) in tissues

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Immune complexes gain access to the bloodstream and are kept in

soluble blood and transported to the liver and spleen

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once transported the immune complexes

are taken up by phagocytes (such as Kupffer cells) and are destroyed

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immune complexes can be

physiological or pathological

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the end result of abnormal immune complexes is that they are

precipitated out of tissues and cause inflammation

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Serum sickness

immune complexes are deposited throughout many tissues

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Arthus reaction

complexes form locally in tissues

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Type IV

no antibody component

mediated by Th1 cells and the cytokine products (eg IL2 etc)

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Type IV takes places because the immune system finds it difficult to

destroy environmental agents

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in hypersensitivity - there is no major effect by the environment agents. the damage is don't to the tissue by the

immune response

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low molecular weight agent

HAPTEN

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host protein

CARRIER

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type IV has a delay of

48-72 hours

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Hapten and carrier + microorganism

antigen uptake which gives..



Th1 antigen + cytokine production which leads to INLFAMMATION

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Autoimmune disease is mediated through aberrant cellular immunological mechanisms which are directed against

autoantigens

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Tolerance

process by which the immune system avoids producing damaging reactions against self antigens

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breakdown of one or more of the processes of tolerance leads to

autoimmune disease

34

effector mechanisms involved in autoimmune disease

cellular T cell and B cell activity

antibody activation of complement-mediated inflammation

immune complex formation

recruitment of innate immune components

35

2 important contributors to autoimmune disease

HLA allele

environmental factors (including infection)