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Alterations in immune function
Patho Test 2
34
Pathology
Undergraduate 1
02/20/2012

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Term
Autoimmunity
Definition

o   Immune system attacks own tissue. An individual’s immune system recognizes its own cells as foreign and mounts an immune response that injures self tissues.

Term
4 theories of autoimmunity
Definition
  • Antigenic mimicry theory
  • Release of sequestered antigens
  • T-cell theories
  • B-cell theories
Term
Antigenic mimicry theory
Definition

§  Self/foreign antigens made of same materials, so alterations in self tissue lead to attack

Term
Release of sequestered antigens
Definition

§  Self antigens not in direct contact with lymphocytes during fetal development

§  Antigens “hid” in places lymphatics couldn’t reach, when illness hits, Ag’s released

Term
T-cell theories (autoimmunity)
Definition

§  Thymus gland defects

§  Decreased suppressor T-cell function

§  Altered T helper cell function

Term
B-cell theories (autoimmunity)
Definition

§  B cells lose their responsiveness to suppressor T-cell signals: ↑↑ in B cell function and autoAb production

Term
Hypersensitivity
Definition

Ø  : Normal immune response that is:

o   Inappropriately triggered

o   Excessive

Produces undesirable effects on the body

Term
Basic mechanism of hypersensitivity
Definition

o   specific antigen-antibody reaction or specific antigen-lymphocyte interaction

Term
Type 1 hypersensitivity
Definition
Allergice response
Term
Type 1 hypersensitivity: primary Ab and role of intracellular Ca++
Definition

IgE

Increases intracellular Ca++

Term
Type 1 hypersensitivity: how long does it take?
Definition
15-30 min
Term
Type 1 hypersensitivity: Principle WBC, principle chemical mediator
Definition

§  Mast Cell

§  Histamine: causes increased vascular permeability, vasodilation, urticaria, smooth muscle constriction (asthma!), increased mucus secretion, pruritus

Term
Type 1 hypersensitivity: Steps of reaction (7)
Definition

§  Ag (antigen) exposed to B cells

§  B cells crank out IgE

§  Ige binds to mast cells (covered with IgE receptors/vesicles filled with vasoactive substances)

§  Exposure of mast cell to Ag→IgE and Ag’s crosslink

§  ↑ intracellular Ca+2

§  Degranulation

§  Inflammation 

Term
Type 1 hypersensitivity: clinical manifestations (mild, moderate, anaphylaxis)
Definition

§  Mild

·         Hives

·         Seasonal allergic rhinitis

·         Eczema

§  Moderate

·         Throat constriction

·         Wheezing

·         Tachycardia

§  Anaphylaxis

·         Most life-threatening reaction; occurs in very small number of highly allergic individuals

Term
Type 2 Hypersensitivity: 
Definition
Term
Type 2 Hypersensitivity: primary Ab's involved
Definition
IgG or IgM
Term
Type 2 Hypersensitivity: How is tissue damage accomplished?
Definition

§  Antibodies attack antigens on surface of specific cells or tissues 

Term
Type 2 Hypersensitivity: antigens and Ab's associated with blood types
Definition

§  Type A

·         A Ag and B Ab

§  Type B

·         B Ag and A Ab

§  Type AB

·         A/B Ag and no Ab

§  Type O

·         No Ag and A/B Ab

Term
Type 2 Hypersensitivity: Erythroblastosis fetalis (mechanism)
Definition

§  Rh-neg mother is pregnant with Rh+ baby → blood mixes at delivery → mom makes antiRh-Ab → (next pregnancy) Rh-neg mother pregnant with Rh+ baby → mother’s IgG crosses placenta and attacks fetal blood cells

Term
Type 3 Hypersensitivity: 
Definition
Immune complex reaction
Term
Type 3 Hypersensitivity: primary Ab involved
Definition
IgG
Term
Type 3 Hypersensitivity: How does tissue damage occur?
Definition

§  Immune system is unable to get rid of Ab-Ag complexes, complexes deposit in tissue and complement/neutrophils are activated which results in the release of enzymes and free radicals resulting in tissue destruction 

Term
Type 3 Hypersensitivity: Where do complexes collect
Definition
Kidneys
Term
Type 4 Hypersensitivity:  
Definition
Delayed hypersensitivity
Term
Type 4 Hypersensitivity: Principal mediators
Definition
Killer T-cell
Term
Type 4 Hypersensitivity: what is hapten?
Definition
Incomplete, lipid soluble antigen
Term
Type 4 Hypersensitivity: describe the mechanism (6)
Definition

§  Hapten binds with another ‘carrier’ protein (hapten+protein=complete Ag)

§  Ag taken up by Ag-presenting cell

§  Taken to lymph node

§  Presented to Th cells

§  Lymphokines released

§  Inflammation→destruction

Term
Type 4 Hypersensitivity: which branch of immune response?
Definition
Adaptive, so it takes time
Term
Type 4 Hypersensitivity: how is tuberculosis a type 4 hypersensitivity reaction? what happens?
Definition

§  The Ag is not destroyed by macrophage→triggers inflammatory response→ immune cells begin to collect and build up forming a giant multi-nucleated cell (granuloma)→ granuloma becomes fibrotic→ central necrosis (caseous)

Term
Chronic mucocutaneaus candiasis
Definition

o   Autosomal recessive; a selective deficiency of cell-mediated immunity against C. albicans

Term
Primary immunodeficiency disorder
Definition

§  May be from congenital, genetic, or acquired defects that directly affect immune cell function

§  First clinical indicators: signs and symptoms of infection

§  Suspected with severe recurrent, unusual, or unmanageable infections

§  Most cause moderate immune impairment that may not be diagnosed

§  Severe congenital immunodeficiency disorders less common, clinically significant

Term
Secondary immunodefiency disorder
Definition

§  Problems in neuroendocrine and immune system interaction

§  Excessive neuroendocrine response to stress; increased corticosteroid production increases susceptibility to infection

§  Immune function impaired as a result of other non-immune system disorders that secondarily suppress immune function

·         Poor nutrition

·         Stress

·         Drugs 

Term
Self-tolerance
Definition

o   Self-tolerance=recognition; so autoimmunity= break down of self-tolerance 

Term
SCID
Definition
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