Final- Hypersensitivities Flashcards
What is the definition of a Hypersensitivity?
response to an Ag that is beyond normal
What are the four types of Hypersensitivity Reactions?
- Type I (immediate/allergies)
- Type II (antibody/cytokines)
- Type III (immune complex)
- Type IV (cell mediated/delayed)
“ACID”
T/F. Only some forms of Hypersensitivity require prior exposure to the antigen.
False– ALL forms require prior exposure
What type of antibodies or cells are involved in each one of the Four hypersensitivites?
- Type I –> IgE
- Type II –> IgM and/or IgG
- Type III –> IgM and/or IgG
- Type IV–> T cells
How much time does it take before clinical signs show up for the each one of the 4 types of hypersensitivities?
- Type I –> less than 30 mins
- Type II –> 5-12 hrs
- Type III –> 3-8 hrs
- Type IV –> 24-48 hours
What type of Hypersensitivity is rapid and always involves IgE and the degranulation of basophils or mast cells?
Type I (anaphylactic/ allergies)
What type of Hypersensitivity involes IgM or IgG antibodies binding ot cell membranes or ECM and the Ag may be you or exogenous molecules?
Type II (cytokine)
What type of Hypersensitivity involves IgM or IgG antibodies binding to soluble Ag’s and forming an anitbody complex and inflammation takes place at sites of deposition of the complexes?
Type III (immune complexes)
What type of Hypersensitivity involves direct attack of WBCs w/o using antibodies and T cells initiate the inflammation?
Type IV (delayed type)
What type of hypersensitivity is anaphylactic shock from drug injection and insect venom an example of?
Type I
What type of hypersensitivity is arthus reactions or serum sickness an example of?
Type III
What type of hypersensitivity is transfusion reactions and Rh incompatibility an example of?
Type II
What type of hypersensitivity is a rejection of transplanted tissues, contact dermatitis,– like poison ivy, or certain chronic diseases such as Tb examples of?
Type IV
What occurs on the initial exposure for a Type I hypersensitivity?
- allergen enters body
- APC eats it
- APC presents peptides from allergen on MHC II’s
- Helper T cells are activated –> differentiate into the Th-2 subtype (GI system and parasites)
- Th-2 cells activate B cells that are specific for allergen
- B cells (plasma cells) make IgE specific to allergen (Ag)
When an individual is first exposed to an allergen, do they have a reaction?
may not have initial allergic reaction; it takes time for IgE antibodies to accumulate and load onto mast cells
For a Type I Hypersensitivity describe what is occurring during Sensitization. What will a second exposure cause?
- IgE antibodies’ Fc regions bind w/ high affinity to mast cells (which are everywhere in body)
- Second exposure will ACTIVATE mast cells and degranulation will occur
What occurs during Re-Exposure for a Type I Hypersensitivity?
allergen will bind to IgE antibodies which are attached to Mast Cells via there Fc region —-> this will cause degranulation of mast cells and release of chemistry
What does the chemistry released by mast cells during the allergic reaction of a Type I hypersensitivity include?
- vasocative amines (histamine)
- prostaglandins
- leukotrienes
- recruitment of other WBCs (neutrophils and eosinophils)
- leaky vessles, edema, smooth muscle spasms, increased mucus secretion, drop in BP
What “type” of a Type I hypersensitivity involves being injected via insect sting and may result in shock which could be deadly?
Systemic Anaphylaxis
What “type” of a Type I hypersensitivity involves generally ingested or inhaled, but could be systemic?
Localized Anaphylaxis
What are examples of upper respiratory Type I Reactions? How are they Tx?
(hay fever)
- itchy eyes, congestion, sneezing
- pollen, pet dander, dust mite feces
Tx: antihistamine
What is an example of a lower respiratory Type I reactions? How is it Tx?
- asthma
Tx: epinephrine, albuterol
What are some common causes and symptoms of a Gastrointestinal Type I reaction?
NOT food intolerance!!!!
Causes: Eggs, peanuts, tree grown nuts, milk, soy, fish, wheat, peas
Symptoms: hives
How can one prevent a Type I reaction? What is short term Tx for it? What is long term Tx?
avoid contact and get a skin test to Dx
Short term–> antihistamine and epinephrine
Long term–> desensitize and convert IgE and IgG
How are Type II hypersensitivities mediated?
antibody mediated by IgM or IgG (NOT IgE)
What do the antibodies bind to that are involved in a Type II reaction?
surface of cells (cell membrane) or the ECM
What are the two means of destruction for Type II reaction?
- Antibody-dependent cell -mediated cytotoxicity (ADCC)
2. Complement system
Which hypersensitivity is the ADCC involved in? What is it? What occurs?
Type II
Antibody-dependent cell-mediated cytotoxicity
WBCs w/ Fc receptors (monocytes, neutrophils, eosinophils, and NK cells) bibind to cells with IgG or IgG antibodies
What type of hypersensitivity involves the Complement system? What
Type II and Type III b/c IgM and IgG are good at fixing complement
What does activating the Complement system for Type II and Type III reactions result in? What Ab are involved?
IgM and IgG are good at fixing complement
- complement proteins may destroy the cells (MACs)
- Products of the complement proteins activate macrophages and neutrophils
What type of hypersensitivity is Hemolytic Disease of the Newborn? When does this occur?
Type II reaction
Rh+ father and Rh- mother make Rh+ baby–> 1st child = no issue; 2nd child she has developed Ab’s against Rh now = issues
Mother must take RhoGAM in order to prevent her Ab.s from attacking fetus RBCs
What is occurring in a Type III reaction?
Antibody-Antigen Complexes accumulate and are deposited in tissues and cause inflammation
(normally they would be cleared, but here they attempt to be, but can’t be = inflammation)
Complement System
Where are the deposition of antibodies and antigen complexes that occur in a Type III reaction typically?
- vascular walls –> vasculitis
- other tissues–> arthritis
- common in kidneys and joints
What type of hypersensitivity is vasculitis an example of? How does this occur?
Type III
phagocytes get attracted due to deposition of antibody-antigen complexes–> and cause inflammation by releasing cytokines
What hypersensitivity is Rheumatoid Arthritis an example of?
Type III–> caused by Ab complex deposition into joints
What type of hypersensitivity is an excessive or inappropriate immune response from T cells? What is another name for this reaction?
Type IV
DTH = Delayed Type Hypersensitivity
What mediates a Type IV reaction?
T cell mediated w. help from:
- CD4 helper T cells
- CD8 killer T cells
- macrophages
- neutorophils
T/F. Type IV hypersensitivity involves antibodies.
False– it does NOT; it involves T cell mediated response
What are Type IV reactions directed against, self or exogenous antigens?
BOTH
What type of hypersensitivity is Poison Ivy an example of?
Type IV
T/F. All four types of hypersensitivity occur upon second exposure.
True
