Lecture 18 Flashcards
Ch 14 allergy and the immune response to paraasites
What are some common causes of hypersensitivity reactions?
pollen, insect venom, peanuts, plant oil
What Ab mediates a type I hypersensitivity reaction?
IgE
What immune responses defend the body against infestation against multicellular parasites?
Th2 immune responses
What Ab are involved in a Th2 response?
IgE, IgG1, and IgG4
What behaviors can prevent proper development of the immune system in children?
excessive hygiene, vaccination, and overreliance on antibiotics
Describe the Type I hypersensitivity.
It is IgE mediated, cells are coated with the Ab and when Ag binds, it crosslinks the Fc receptors on mast cells and basophils and induces degranulation
What is sensitization?
Sensitization happens during the first exposure to an allergen… the B cell delivers the allergen to a Th2 cell which leads to the development of Ab against the allergen in plasma and mast cells (these cells are now “pre-loaded”) that will degranulate immediately next time the host is exposed to the same allergen
Define atopy.
Allergy
What is the difference between atopic and non-atopic individuals?
Atopic individuals have a hereditary disposition to develop a type I response and contain 10X higher levels of IgE
Non-atopic individuals have significant IgE responses ONLY in defense against parasites
Where do most allergic responses occur?
On mucosal surfaces
Define allergen.
A nonparasitic Ag that causes an inappropriate IgE response and type I hypersensitivity
Define allergenicity.
Ability to evoke a Th2 response
What are some common IgE-mediated allergic reactions?
systemic anaphylaxis, hay fever, asthma, food allergy
When to mast cell precursors differentiate into mature cells?
When they migrate into peripheral tissues from the blood
What must happen to induce a signal and cause degranulation when IgE binds to Fc?
The allergen must cross-link the IgE-receptor complex
What receptor do mast cells on mucosal surfaces express?
Fc-epilson-RI
What happens when histamine binds to H1?
Induced contraction of intestinal and bronchial smooth muscle, increased venule permeability, increased mucus secretion
What can block H1 receptors?
Antihistamines!
What is important about granulocyte evolution?
They evolved to kill parasites
Describe localized type I reactions.
Limited to a specific target tissue, involves epithelial cells at the site of allergen entry
Describe systemic Type I reactions.
Systemic anaphylaxis occurs by the allergen is directly introduced into the bloodstream, IgE-coated mast cells throughout the body are all activated, casuing mass loss of blood pressure, reduced O2 to tissue, difficulty swallowing and breathing
How can type I hypersensitivity be detected?
Skin test
What are some strategies to treat or prevent allergic reactions?
A patient environment can be modified to prevent allergies, antihistamines, epinephrine to treat anaphylaxis, and desensitization
Describe the type II hypersensitivity.
It is an antibody-mediated cytotoxic hypersensitivity where the Ab bound to the cell surface Ag is recognized by the Fc receptor on cytotoxic cells
