Q.No.4. What part do antibiodies play in allergic reaction? How vaccination can be helpful in its control/prevention? (10)

Ans.

Definition
By Mayo Clinic Staff
Allergy shots are a form of treatment called immunotherapy. Each allergy shot contains a tiny amount of the specific substance or substances that trigger your allergic reactions. These are called allergens. Allergy shots contain just enough allergens to stimulate your immune system — but not enough to cause a full-blown allergic reaction.

Over time, your doctor increases the dose of allergens in each of your allergy shots. This helps get your body used to the allergens (desensitization). Your immune system builds up a tolerance to the allergens, and your allergy symptoms diminish over time.

So this could be categorised as a kind of vaccination.

Typically Allergy is regarded as Hypersensitivity 1 reaction in which the major role player is the antibody Immunoglobulin-E.(Ig-E).

Pathophysiology of an Anaphylactic reaction is as given

Antigen > Antigen Presenting Cell (presents the antigen for physiological response) > T-cell Stimulation > IgE production from B-cells > Fc receptor of Basophills+Mast Cells> Histamine and other inflammatory mediators > Vasodilation , Mucus secretion etc.

Introduction of Allergen again > IgE cross linking Fc > Binding of allergen to more then one complexes > Response anew.

Conventional Therapy is the symptomatic one.

Anti-histamine
Corticosteroids
NSAIDS
or Supportive
Fluid therapy to dilute allergen
Blood Transfusion
Toxin-binding solutions (Veterinarians use Calcium based solutions with calcium being a binding/chelating entity)
It will not eliminate the aetiological agent(cause) but will subside the symptoms.

Allergen Immunotherapy

Mechanism is to trigger cell-mediated immunity instead of humoral immunity. It makes possible commencement of Phagocytic activity plus modified humoral response.
IgE production is skewed.

Recent Scenario:

Pure allergens are not used as there is a risk so instead the modified ones are used which are less likely to illicit the acute response.

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