Hypersensitivity Flashcards
Hypersensitivity is dependent on
Presence of an antigen and T cell sensitized to antigen
Hypersensitivity Type 1 is an …
IgE mediated immediate hypersensitivity reaction
3 types of type 1 hypersensitivity
- Allergic reaction
- Anaphylaxis
- Atopic hypersensitivity
Type 1 hypersensitivity reaction time
15-30 mins
Biphasic reaction
A second reaction, that usually occurs within 8 hours of the initial reaction, but may occur 24 to 72 hours post exposure
Hypersensitivity Type 1 reaction manifestations (7)
Itching, localized swelling, throat tightness, wheezing, SOB, tachycardia, hypotension
List 6 Steps to Hypersensitivity Type 1 Pathogenesis
- First exposure to antigen results in APC attaching to helper T cell, presenting antigen on MHC2
- Class switching results in antibody IgE production instead of IgG or IgM
- All of the IgE antibodies bind to Fc receptors on mast cells (mast cell sensitization)
Second exposure
- Antigen (allergen) binds to mast cells and cross links with other antibodies
- Degranulation of mast cells and lots of release of histamine
- Signs and symptoms of inflammation
Primary early response symptoms of hypersensitivity type 1(3)
Vasodilation
Vascular damage
Smooth muscle spasm
Second late response symptoms of hypersensitivity type 1 (5)
mucosal edema
mucous secretion
leukocyte infiltration
epithelial damage
bronchospasm
Hypersensitivity Type 2 is a …. reaction… also known as ….
immediate hypersensitivity reaction also known as cytotoxic or cytolytic hypersensitivity
Hypersensitivity Type 2 reaction time
15-30 mins
Two examples of type 2 hypersensitivity reaction
ABO transfusion reaction
Hemolytic disease of the newborn
3 Steps of Hypersensitivity Type 2 Patho
- Triggers by exposure to antigen on surface of foreign cells
- IgG or IgM antibodies bind to antigens to form antigen-antibody complex
- Antigen-antibody complex initiates the complement cascade via classic pathway. MAC (C5-C9) lyses the foreign cells
Hypersensitivity type 3 is also known
as an immune complex mediated hypersensitivity reaction
Why does hypersensitivity type 3 occur?
Typically occurs due to exposure to an excessive amount of antigen usually over a prolonged
period of time such as in the case of a persistent infection
Where can hypersensitivity type 3 occur?
glomerulonephritis (kidney), rheumatoid arthritis (joint), and
in systemic lupus erythematosus (many organs)
Pathogenesis of type 3 hypersensitivity
- Antigen forms antigen-antibody complexes that precipitate out of fluid and deposit into tissue
- Most antigen-antibody complexes are removed before they can cause harm, but in this instance they don’t and lead to tissue injury
- Deposition of immune complexes on tissue result in enzymes being released and activation of complement = surrounding cells get injured too
Glomerulonephritis patho example
Small complexes are removed more easily from the body but in the case of glomerulonephritis the complexes are not able pass through the glomerular basement membrane and into the urine.
The large Ag-Ab complexes become lodged in the glomerular
capillary wall and are phagocytized because they are easily marked due to their size causing injury to the glomerular basement membrane
What is type 4 hypersensitivity?
Cell mediated hypersensitivity response controlled by T lymphocytes, no antibodies involves
Time line of hypersensitivity type 4?
The reaction peaks 24 to 72 hours but can last as long as 14 days after exposure to the antigen
4 examples of hypersensitivity type 4
- contact dermatitis
- tb skin test
- granuloma formation
- graft vs host disease
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