Immunology Flashcards
Allergic asthma occurs in what type of individuals? What’s the mechanism that triggers the reactions seen in those with allergic asthma, what immune cells mediate the inflammation seen in these patients?
Previously sensitized
IgE Ab bound to mast cells in 50% cases. Type I hypersensitivity
Th2 cells mediate airway inflammation
How does someone become sensitized to an antigen/allergen?
APC presents the Ag to a CD4+ T cell
IL-4 causes the differentiation of T-cells to Th2 lymphocytes
Th2 cells activate, B-cells which class switch Ab to IgE
IgE binds mast cells and releases (among other things) pro-inflammatory cytokines and IL-4 which is a positive feedback mechanism
Which of the following can be protective against the development of allergy induced asthma?
1) beets
2) pollen
3) viruses
4) bacteria
5) yeasts
3-viruses b/c they stimulate Th1 response
This has lead to the hygiene hypothesis which says that lack of exposure to infections in early childhood leads to increased risk of allergies; esp true in first world countries. Babies have a biased to Th2 response which maybe balanced by increased Th1.
What is atopy?
Exaggerated tendency to form IgE to a variety of environmental Ag. It has a strong genetic component, patients often present with Eczema, asthma, allergic rhinitis.
what are some genes involved in the immune and systemic response of asthma?
immune- IL-4 induce Th2 differentiation
systemic- B2 adrenergic receptor, lipooxygenase
How does IL-4 participate in Ab class switching?
It activates the enzymes responsible for switching the constant region of the Ig gene.
What’s required for activation of a mast cell?
Cross linking of the IgE molecules to a specific Ag will activate the cell. Not all IgE molecules have the same specificity so it may take time for cross linking to occur.
What effect does mast cell degranulation have on the GI, Airways, and blood vessels?
GI- fluid secretions increased peristalsis
Airways- increased mucus secretions decreased diameter
Blood vessels- increased flow and permeability (hypotension)
Which of the following is part of a mast cells preformed granule and which is only available after mast cell stimulation?
Histamine
Arachidonic acid
IL-4
TNF-alpha
Histamine-preformed granule
all the rest are from cell stimulation
Compare and contrast early and late asthmatic response
early-10-15 mins post inhalation, degranulation of mast cells: airway constriction due to histamine, vasodilators in the vessels
late 3-4 hrs post inhalation: cytokines and eosinophil products cause chronic response
Describe the immunotherapies that could be used to treat asthma and what parts of the sensitization process they would target.
Target Th2 activation by inducing Tregs with TGF beta
Target activation of B-cells and class switching to IgE by blocking the co-stimulation (block Th2 cytokines)
Target mast cell activation by inhibiting the effects of IgE binding to mast cells
Target mediator action by inhibiting their synthesis with antihistamine and lipooxygenase inhibitors
Target Eosinophil-dependent inflammation by blocking cytokine receptors that mediate their activation
