hx4 pharm 11
TRANSCRIPT
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Objectives
After working through this module, you should be able
to:
Explain the immunological mechanisms underlyingtype IV hypersensitivity reaction.
Describe the principal causes and symptomsassociated with type IV hypersensitivity reactions.
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Type IV Hypersensitivity
Type IV hypersensitivity is also known as delayed
type hypersensitivity
It is different from the other 3 types ofhypersensitivity as it represents tissue damageresulting from inappropriate cell-mediated
immunity reactions
Clinical conditions - tuberculosis, leprosy, contact
dermatitis
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Type IV hypersensitivity
T cell
Antigen
ILs
Macrophage
Cytokines
Target cell
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Type IV Hypersensitivity
Initiated by the interaction of antigen with primed
T-lymphocytes and subsequently the release ofsoluble cytokines from the T lymphocytes which
activate macrophages
Activated macrophages may differentiate into
giant cells and develops into granulomantous
hypersensitivity
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Type IV Hypersensitivity
Within the type IV response there are 4 different
phenomena which rarely occur separately. Theseare:
i. Jones-mote reaction
ii. Contact hypersensitivity
iii. Tuberculin reaction
iv. Granulomatous reaction
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Type IV Hypersensitivity
i. Jones-mote reaction
- induced by contact with allergen but is
characterized by the infiltration of basophilsinto the inflammatory site.
- the factors which cause this particular
component of the reaction are unknown
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Type IV Hypersensitivity
iii. Tuberculin reaction
This type of hypersensitivity is the basis of the
Mantoux Test ( 72 hours- check for hard at
injection site)
The basis of tuberculin response is the re-activation of antigen-specific memory T cellswithin the dermal layer of the skin
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Type IV Hypersensitivity
iii. Tuberculin reaction (cont)
T cells produce TNF- local vascularendothelial cells induce infiltration ofneutrophils into the skin
Predominant infiltrating cells mononuclearleukocytes (lymphocytes and monocytes)
reaching a peak at about 48 hours
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Type IV Hypersensitivity
iii. Tuberculin reaction (cont)
Characteristic induration is a result of
combination of large number cells with oedema
Signs of reaction resolve after 5-7 days
In contrast to infection with constant source of
infection, reaction progresses to granulomatous
lesion
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Type IV Hypersensitivity
iv. Granulomatous reaction
Alternative name for granulomatous
hypersensitivity is chronic inflammation
Hallmark of chronic inflammation is mononuclear
cells (monocytes, macrophages, lymphocytes)
This type of DTH has most severe consequences
due to presence of often extensive tissue damage
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Type IV Hypersensitivity
iv. Granulomatous reaction (cont)
2 types of granuloma:
- foreign-body granuloma:
initiated by inert foreign bodies
- immune granuloma:
T cell-mediated reaction to immunogenic
particles
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Type IV Hypersensitivity
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References
Roderick Nairn and Matthew Helbert. Immunology for Medical
Students. Elsevier Mosby. 2003.
Stites DP, Terr Al and Parslow TG. Medical Immunology. 10th Edition,Appleton & Lange, Prentice-hall International Inc. 2001.
Roitt I, Brostoff J and Male D. Immunology. 6th Edition, GowerMedical Publishing, London. 2001
Cedric Mims, Hazel M. Dockrell, Richard V.Goering, Ivan Roitt, Derek
Wakelin and Mark Zuckerman. Medical Microbiology. 3rd
Edition,Elsevier Mosby. 2004.
Marjorie Kelly Cowan and Kathleen Park Talaro. Microbiology ASystems Approach. McGraw-Hill. 2006.