15 Hypersensitivity Flashcards
(42 cards)
What is Hypersensitivity?
Exaggerated immune response that causes damage to the individual
What is immediate hypersensitivity?
an exaggerated immune response mediated by an antibody or antigen-antibody complexes that manifests within minutes - hours after exposure to an antigen
What is the Type I immediate hypersensitivity?
IgE-mediated hypersensitivity
What is the Type II immediate hypersensitivity?
IgG or IgM-mediated hypersensitivity
What is the Type III immediate hypersensitivity?
Immune complex-mediated hypersensitivity
What is delayed-type hypersensitivity (DTH)?
a type-sensitive response that is mediated by T helper cells that release various cytokines/chemokines
When does DTH response take place?
generally 2-3 days after T helper cells interact with an antigen
What is the Type IV DTH hypersensitivity?
cell-mediated hypersensitivity (T cells)
What are the four types of hypersensitivity reactions?
Type I: Allergy and Atopy
Type II: Antibody-mediated hypersensitivity
Type III: Immune complex-mediated hypersensitivity
Type IV: Delayed-type hypersensitivity
What is an allergy?
An allergy is a type I hypersensitivity reaction
What is responsible for type I hypersensitivity?
IgE antibodies interact with a multivalent antigen, so, IgE antibodies
How do allergies come to be?
IgE antibodies cross-link Fcε receptors on the surfaces of innate immune cells, and granule contents are released, like histamine, heparin, proteases, leukotrienes, prostaglandins, and chemokines. Mediators act up on surrounding tissues and cells which causes the symptoms of allergies. (Note: Abs are not harmful by themselves, it’s the linking of the Fcε receptors via IgE antibodies which is why they are the cause of allergies)
What are allergens?
Specific type of antigen that induces a type I hypersensitivity reaction. Examples: nuts, milk, dust mites, penicillin, birch trees
Atopy
Abnormality in people that causes a predisposition to generate IgE Abs against common environmental antigens. Normally, IgE response is against parasitic infection.
Where are mast cells located?
Tissue
Where are basophils located?
They are in circulation throughout the immune system and are recruited into inflammatory sites
What helps Abs when fighting against immune reactions?
Granule contents (histamine, heparin, proteases) and mediators around the affected tissues/cells that cause symptoms
What is the high-affinity IgE receptor? What does it do?
FcERI, responsible for most allergy symptoms; found on basophil/mast cells
What is the low-affinity IgE receptor? What does it do?
FcERII, regulates production of IgE by B cells
True or False: Innate immune cells produce molecules responsible for Type I hypersensitivity symptoms
TRUE.
What are the steps of response from Type I hypersensitivities?
Early response: within minutes of allergen exposure, mediated by mast cell granule contents
Late response: hours later from recruited inflammatory cell types (ex. neutrophils)
Third phase: 3rd day after exposure, peaks at 4th day post-exposure. Massive eosinophil infiltration
What is systemic anaphylaxis? What is it caused by? What cures it?
Shock-like, often fatal state with a within-minutes onset. Caused by venom (bee, ants), drugs (insulin, penicillin), or food (seafood, nuts). Cure: epinephrine
What is anaphylaxis?
Serious allergic reaction with rapid onset that may cause death
What are some examples of localized hypersensitivity reactions (atopy scenarios)?
Hay fever, asthma, eczema, and food allergies
