Lecture 26- Hypersensitivity and Immune Disorders Flashcards
What are the 4 types of immune hypersensitivity reactions?
TI: allergic reactions
TII: lysis of foreign cells
TIII: immune complex reactions
TIV: cell-mediated (delayed) reactions
What is the mechansm of Type I HS?
When IgE contacts allergen it triggers mast cells to release inflammatory mediators (histamine granules, prostaglandins and other cytokines)
Why is type I hypersensitivity called “immediate” even though it only develops after multiple contacts with an allergen?
Once it has developed, any contact with the allergen has immediate effects
Why are antihistamines an effective allergy treatment?
have the same receptors
How can a person be “desensitized” to an allergen?
by multiple injections of the allergen (IgG produces which compete)
by anti-IgE antibodies
What are the symptoms of a typical allergic reaction?
Hives, hay fever, asthma, and generalized anaphylaxis
What causes Type II HS reactions?
haptens or non-native surface proteins which are bound by antibodies (activate complement system)
What is the problem of RH antigen incompatability?
If fetus are Rh+ and mothers are Rh-, it can affect the second fetus
What leads to Type III HS reaction?
formation of immune complexes
Compare Type I and Type IV HS?
In both: First encounter is a sensitization, second exposure leads to reaction
Type I are B cell responses
TIV is mediated by Th cells and macrophages AND response peaks in days, not minutes
What are three examples of Type IV HS reactions?
Poison ivy, tissue rejection, metal “allergy”
What is an autoimmune disease?
failure of the immune system to recognize “self”
Myasthenia gravis
B cells recognize acetylcholine receptors, IgG neutralize receptors, muscles cannot contract
Type I diabetes
TCR on Tc cells recognize beta islet cells in pancreas, beta cells destroyed, no insulin is produced
Rheymatoid arthritis
Th cells recognize collagen in joints and produce cytokines (inflammation
B cells activated, immune complexes form (Type III HS)
