Exam 5 Hypersensitivity Chapter 14 Flashcards
Hypersensitivity definition
an exaggerated immune response to a typically harmless antigen
What are the four categories of hypersensitivity
type I, type II, type III, type IV
What are immediate reactions and what categories of hypersensitivity are immediate reactions
They develop in minutes to hours after antigen exposure and are mediated by antibodies
Type I, Type II, Type III are all immediate reactions
What are delayed reactions and what categories are a delayed reaction
Clinical manifestations don’t develop until 24 to 48 hours after antigen exposure and they are mediated by sensitized T cells
Type IV is a delayed reaction
What is type I hypersensitivity typically thought of as and what is it also known as
Typically thought of as allergies and also known as anaphylactic or immediate hypersensitivity because it occurs within minutes after exposure to an allergen
What are the key components of Type I hypersensitivity
IgE ANTIBODY, mast cells, basophils, and eosinophils
What are the 3 major phases of Type I hypersensitivity
sensitization phase, activation phase, and effector phase
What happens in the sensitization phase in Type I hypersensitivity
IgE bind to the Fc receptors on mast cells and basophils
What happens in the activation phase in Type 1 hypersensitivity
allergen cross-links adjacent cell-bound IgEs, mast cells and basophils degranulate, and histamine and heparin are released to bind to target organs
What happens in the effector phase in Type 1 hypersensitivity
allergy symptoms are produced: Asthma, Eczema, Hay fever, Hives, Anaphylaxis etc.
What are some clinical manifestations of Type I hypersensitivity and what is the most immediate reaction
common allergies like peanuts, shellfish, latex (both Type I and iV) Rhinitis (HAY FEVER), allergic asthma, urticaria (HIVES)- wheal and flare reaction, eczema, and ANAPHYLAXIS - the most immediate hypersensitivity reaction
How can Type I hypersensitivity be treated
using drug therapy like antihistamines, monoclonal anti-IgE antibody, and allergy shots
How is Type I hypersensitivity tested for
in vivo skin tests that evaluates the cellular immune response, a positive test = wheal and flare at the site of application
What is Type II hypersensitivity known as and what type of hypersensitivity is it
it is known as antibody-mediated cytotoxic hypersensitivity, it is immediate
What type of antibodies are in Type II hypersensitivity
IgG and IgM antibodies, they are directed against a cell surface antigen
What are the effects of the antibodies in Type II hypersensitivity
cell destruction due to complement
What are some clinical examples of Type II hypersensitivity
reactions involving red blood cell antigens such as transfusion reactions, hemolytic disease of the newborn (HDN), and autoimmune hemolytic anemia
What happens during transfusion reactions, hemolytic disease of the newborn, and autoimmune hemolytic anemia
during a transfusion reaction a patient is transfused with blood (antigens) which combine with their antibodies
during HDN mothers make antibodies against baby’s cells
during autoimmune hemolytic anemia individuals form antibodies to their own RBCs
What are the types of tests for Type II hypersensitivity
the Direct Antiglobulin Test (DAT) and the Indirect Antiglobulin Test (IAT) aka Coombs’ test
DAT detects RBCs coated with complement components or IgG antibody, patient RBCs are incubated with a poly-specific anti-human Ig directed against IgG and C’
The IAT tests patient serum for antibodies to RBC antigens
What is Type III hypersensitivity known as and what type of hypersensitivity is it
it is known as the Complex-mediated hypersensitivty and it is immediate hypersensitivity
What are the key components of Type III hypersensitivity
IgG and IgM antibodies directed against a soluble antigen, small antigen-antibody complexes precipitate out and deposit in tissue, this process results in complement destruction*
What is the arthus reaction
a skin reaction characterized by antigen-antibody complex deposits in the blood vessels in the skin, and can be seen in humans after booster injections with tetanus, diphtheria, or measles vaccines
What is serum sickness
it is caused by passive immunization of humans with animal serum and symptoms appear 7 to 21 days after injection
Seen more often before vaccines and antibiotics: patient treated with horse anti-serums for diphtheria, pneumonia, tetnus, etc
What are some autoimmune diseases associated with Type III hypersensitivity
systemic lupus erythematosus (SLE)* or rheumatoid arthritis (RA)* and GpA sequelae infections* such as post-streptococcal glomerulonephritis
How can Type III hypersensitivity be tested for
testing for antinuclear antibodies (ANA), testing for rheumatoid factor (an anti-IgG) and testing complement levels
What is Type IV hypersensitivity and what is it also known as
cell-mediated hypersensitivity and it is also known as delayed hypersensitivity, it peaks 48 to 72 hours after antigen exposure
What happens during Type IV hypersensitivity
cytotoxic T lymphocytes (T-cell) are recruited and destroy target cells*
What are some clinical infections associated with Type IV hypersensitivity
