BMD 430 Lecture 12 Hypersensitivity Questions and Answers 100% Verified
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BMD 430 Lecture 12 Hypersensitivity
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BMD 430 Lecture 12 Hypersensitivity
IgE - ️️type 1 hypersensitivity
-IgE antibodies act by cross-linking Fcε receptors on surfaces of immune cells
-Ig's not harmful by themselves; low levels in circulation
-Harm comes from interactions with Fcε receptors on effector cells
-*Effector cells release granules*
-*Granules conta...
BMD 430 Lecture 12 Hypersensitivity
IgE - ✔️✔️type 1 hypersensitivity
-IgE antibodies act by cross-linking Fcε receptors on surfaces of immune cells
-Ig's not harmful by themselves; low levels in circulation
-Harm comes from interactions with Fcε receptors on effector cells
-*Effector cells release granules*
-*Granules contain histamine, heparin, proteases, leukotrienes, prostaglandins,
chemokines -very bioactive*
-Mediators act on surrounding tissues and cells to cause symptoms
Basic model for immunity - ✔️✔️Antigen-into body->recognition-> effector response
Hypersensitivity reactions - ✔️✔️inappropriate secondary responses against (relatively)
harmless antigens
As a result, these immune reactions result in - ✔️✔️more harm than benefit (reaction is
worse than the antigen)
Hypersensitivity types classified by - ✔️✔️1.Time until response (seconds to days)
2.Mechanism (cells and/or molecules responsible)
3.Types of damage caused
Effector stage - ✔️✔️secondary immune response to same antigen
Type 1 hypersensitivity: allergy - ✔️✔️-inappropriate *IgE* response against a
harmless antigen
Most individuals have an immune response against the antigens, but it's usually IgM,
IgA, and/or IgG.
Allergy is also referred to as atopy (atopic reactions; atopic patients)
, Atopic systemic allergy - ✔️✔️anaphylaxis (vasodilation of blood vessels)
Atopic local allergy - ✔️✔️depends on the location (hay fever, hives)
Type 1 What is an allergen? - ✔️✔️-substances that elicit an allergic (type I
hypersensitivity) response
They are usually soluble (glyco)proteins that contain multiple epitopes
They also usually have:
(1)Internal *enzymatic activity* (e.g. a protease)
(2)They may contain PAMPs (DAMPs)or PAMP (DAMPs)-like structures
(3)They usually enter the host through mucosal tissues at very small concentrations
(TH2 → IL-4/IL-13 → IgE)
Atopy - ✔️✔️tendency to develop a heightened immune response against something
normally considered harmless
High affinity IgE FceR1 - ✔️✔️-very very high affinity
-responsible for most allergy symptoms
-constitutively expressed by mast cells, basophils and eosinophils
Low affinity IgE FceR2 - ✔️✔️regulates production of IgE by B cells
-regulating receptor
When IgE binds to both receptors- - ✔️✔️FceR2 wins and shuts down production of
IgE
IgE receptor signaling is tightly regulated; activating and inhibitory receptors are co-
clustered ON EFFECTOR CELLS - ✔️✔️-Mast cells express both FcεR1 (activating)
and FcγRIIB (inhibiting) Ig receptors
-If a cell binds IgE and IgG, the inhibiting signal induced by IgG binding wins
-In part why inducing IgG in atopic individuals ("allergy shots") is effective; also called
desensitization therapy
Type 1 Summary of allergies - ✔️✔️Actions (under normal circumstances):
1.Vasodilation and Vascular Permeability
2.Influx of Plasma mediators and inflammatory cells
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