A patient suffering from allergy has been advised to take anti-histamine drugs. Which one of the following
biological processes is most likely to be the reason for the allergy?
(1) Mast cell degranulation
(2) Thymocyte maturation
(3) Somatic hypermutation
(4) Bystander lysis
Why Anti-Histamines Are Used for Allergies: Understanding Mast Cell Degranulation
If you’ve ever suffered from a runny nose, itchy eyes, or skin rashes due to allergies, you’ve probably been prescribed an anti-histamine. But have you ever wondered why anti-histamines work so effectively against allergy symptoms?
The answer lies in a process called mast cell degranulation—a key immune response mechanism in allergic reactions.
Among the options provided:
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(1) Mast cell degranulation ✅
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(2) Thymocyte maturation
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(3) Somatic hypermutation
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(4) Bystander lysis
The correct answer is (1) Mast cell degranulation.
What Is Mast Cell Degranulation?
Mast cells are a type of white blood cell found in tissues throughout the body, especially at points of contact with the external environment—like the skin, lungs, and digestive tract. These cells play a central role in allergic responses.
When a person with allergies is exposed to an allergen (like pollen, dust mites, or certain foods), the immune system mistakenly identifies it as a threat. As a result:
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IgE antibodies specific to that allergen are produced.
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These antibodies bind to mast cells, sensitizing them.
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On subsequent exposure, the allergen binds to these IgE antibodies.
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This triggers mast cell degranulation—the release of chemical mediators like histamine.
What Happens During Degranulation?
During degranulation, mast cells release a variety of chemical compounds stored in granules, including:
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Histamine – causes vasodilation, increased vascular permeability, itching, and smooth muscle contraction.
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Prostaglandins and Leukotrienes – contribute to inflammation.
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Cytokines – further recruit immune cells to the site.
These chemicals cause the classic allergy symptoms: swelling, itching, redness, runny nose, watery eyes, and even anaphylaxis in severe cases.
How Anti-Histamines Work
Anti-histamines are drugs designed to block histamine receptors, especially H1 receptors, thereby preventing or reducing histamine’s effects. This helps relieve symptoms like:
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Sneezing and nasal congestion
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Itchy eyes and throat
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Skin rashes (hives)
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Runny nose
By preventing histamine from binding to its receptors, anti-histamines target the effects of mast cell degranulation, not the root cause. That’s why they are commonly prescribed for short-term relief.
Misconceptions About Other Options
Let’s briefly address the incorrect options:
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Thymocyte maturation – This occurs in the thymus and is involved in T-cell development, not allergies.
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Somatic hypermutation – Refers to mutations in B cells during antibody production; it’s a part of adaptive immunity but not specific to allergy.
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Bystander lysis – Refers to the accidental killing of nearby healthy cells during immune responses, typically in viral infections.
Summary Table
| Biological Process | Role in Allergy |
|---|---|
| Mast cell degranulation | ✅ Direct cause of allergic symptoms due to histamine release |
| Thymocyte maturation | ❌ Related to T-cell development |
| Somatic hypermutation | ❌ Part of antibody diversity generation |
| Bystander lysis | ❌ Not involved in allergic responses |
Final Thoughts
Allergies are an overreaction of the immune system to harmless substances, and mast cell degranulation is the key event that leads to all those unpleasant symptoms. Understanding this process explains why anti-histamines are such an effective treatment. They don’t stop the allergy itself but block the effects of histamine, the main troublemaker released by mast cells.
So next time you reach for an anti-histamine, you’ll know exactly how it’s helping your body calm down from an allergic reaction.
