Type 1 Hypersensitivity Flashcards
Which Ig subclass mediates Type 1 Hypersensitivity?
IgE
Can someone have an allergic reaction upon their first exposure to an antigen?
Nope
Which subclass of CD4+ T cells are preferentially activated after exposure to allergens? Which cytokines are responsible for this activation? Which cytokines do the activated T cells produce?
IL-4 from APCs activate TH2 T cells, which then make IL-4, IL-5, and IL-13, activating eosinophils and causing differentiation into plasma cells that make IgE
Name four chemicals that mediate early phase Type 1 Hypersensitivity.
Histamine, proteases, leukotrienes, prostaglandins.
What does platelet activating factor do?
Activates platelets!
What role do platelets play in allergic reactions?
They release serotonin, which causes massive vasodilation –> BP drops –> anaphylaxis.
Which cells play a role in the late phase of acute allergic reactions?
Mast cells, TH2 cells, macrophages, and eosinophils release cytokines ~5-6 hours after exposure to the antigen.
What is a RAST test?
A test that measures specific IgE antibodies.
What drug treats acute anaphylaxis?
Epinephrine
What is the basis for hyposensitization treatment?
Small amounts of antigen are injected subcutaneously into the patient so that they build up IgG instead of IgE. Hopefully upon natural exposure to the antigen, IgG that is now in the patient will neutralize Ags before they can degranulate mast cells.
How long does it take to read a skin prick test?
5-10 minutes
Describe two possible reasons why hyposensitization increases IgG over IgE.
- TH1 cells are preferentially activated during the process.
- Hyposensitization may activate Treg cells, turning TH2 cells off.
Can complement proteins, heat, cold, pressure, exercise, CNS effects, and drugs degranulate mast cells?
Yup!
