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Immune disorders
Dr. David Senchina, Drake University, Medical Microbio notes set 10
27
Microbiology
Undergraduate 2
03/07/2010

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Term
Immunopathologies
Definition
Disorders of the immune system.
Term
What are the two groups of immunopathologies?
Definition
Hypersensitivity
Hyposensitivity
Term
Allergy
Definition
A type of hypersensitivity - allergy is NOT interchangeable with hypersensitivity
Term
Hypersensitivity
Definition
An immune system that reacts to particles that are innocuous in non-allergic individuals.
Term
What are the two sources of hypersensitivity?
Definition
Exogenous - allergies
Endogenous - autoimmunity
Term
What is the biological basis for hypersensitivity?
Definition
It's speculated that our immune system is naturally overactive, but now that our environments are so clean, they just find other things to target.
Term
Types I-III hypersensitivity
Definition
Humoral (B-cell)
Term
Type IV hypersensitivity
Definition
Cellular (T-cell)
Term
Type I hypersensitivity
Definition
Immediate hypersensitivity - all reactions are IgE-mediated.
Two types: Atopy (local & chronic), Anaphylaxis (systemic & acute)
All reactions are two-stage.
Term
Allergen
Definition
Usually proteins, but sometimes haptens, that trigger an inappropriate immune response
Term
Hapten
Definition
A very small, nonproteinaceous compound that complexes with other materials to become large enough to be recognized.
Term
What are the common portals of entry for allergens?
Definition
Respiratory system
GI system
Circulatory system
Dermal system
Term
What is the first stage of a type I immune reaction?
Definition
This is the sensitizing dose, during which exposure occurs for the first time, and IgE specific for the allergen binds to a granulocyte, "priming" it for future contact.
Term
What is the second stage of a type I reaction?
Definition
Primed granulocytes come in contact with the allergen and, even though there's nothing to attack, release granules, causing an inappropriate immune response. This causes the symptoms of an allergic reaction.
Term
What are some common forms of atopy?
Definition
Allergic rhinitis (hay fever)
Asthma
Atopic dermatitis (eczema)
Food allergies
Drug allergies (some classify as type II)
Term
Anaphylaxis
Definition
Dose of allergen is much larger, so the magnitude of reaction is much greater. About a third have undetermined causes.
Term
What are the two types of anaphylaxis?
Definition
Cutaneous (wheal-and-flare)
Systemic (circulorespiratory distress)
Term
Type II hypersensitivity
Definition
IgG or IgM triggers a complement cascade that results in cell destruction.
Included in this category are blood type incompatibilities and some types of autoimmunity.
Stimuli are alloantigens - molecules that differ within a species
Term
How are fetuses (allografts) tolerated?
Definition
The placenta serves as a nonimmunogenic tissue and promotes local immunosuppressive responses.
Placenta expresses special MHC molecules that inhibit NK cells, produces immunosuppressive cytokines
Term
Type III hypersensitivity
Definition
IgG or IgM binds to antigens in large volumes, causing them to fall out of circulation, attracting complement. Neutrophils try to clear them, but in order to do so, must clear the surrounding tissue.
Term
Arthus reaction
Definition
Localized dermal response to allergens, through contact or injection. Typically short and self-limiting.
Term
Serum sickness
Definition
Systemic response to injected allergens, which can become chronic.
Term
Type IV hypersensitivity
Definition
T cells react to antigens on foreign or self cells.
Two main types: contact dermatitis and graft rejection
Term
Urushiol
Definition
Active component in poison ivy
Term
Graft rejection
Definition
Type IV hypersensitivity, in which the host rejects the graft or the graft rejects the host.
Term
Autoimmunity
Definition
An inappropriate response to self, sometimes congenital, sometimes developed.
Term
Autoantibodies
Definition
Antibodies that recognize self, produced in small, constitutive levels in everyone, for "self-cleanup" activites.
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