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[Immunology](https://durgical.com/en/immunology/) · [Immune cells](https://durgical.com/en/immunology/#a-cells)

# Mast cell and basophil

- Cell

Mast cells in tissues and basophils in blood carry IgE on their surface and, when an allergen binds it, release histamine within minutes.

Updated 2026-11-01

## Key points

- Both carry FcεRI loaded with IgE; allergen cross-linking triggers degranulation (type I hypersensitivity).
- Preformed mediators: histamine, heparin and tryptase; newly made: leukotrienes, prostaglandin D2 and cytokines.
- Mast cells are tissue-resident and long-lived (skin, airways, gut, around vessels); basophils circulate and are fewer than one in a hundred white cells.
- Mast cells depend on stem cell factor and its receptor KIT (CD117); basophils develop under IL-3.
- Serum tryptase rises in anaphylaxis and in systemic mastocytosis.

## What it is

Mast cells and basophils are related granulated cells that coat themselves with IgE through the high-affinity receptor FcεRI. When an allergen cross-links that IgE, they degranulate, releasing histamine and other mediators that open and leak blood vessels, tighten airways and cause itch. Mast cells live for a long time in tissues at the borders with the outside world; basophils are the rare circulating version.

## Key facts

- Origin: bone marrow; mast-cell progenitors finish maturing in tissue.
- Basophils are the only circulating leukocytes that contain histamine and are an early source of IL-4.
- Mast cells can also be triggered without IgE, by complement fragments (C3a, C5a) and some drugs.

## Step by step

- First exposure: Th2 help leads B cells to make IgE against an allergen.
- IgE binds FcεRI on mast cells and basophils (sensitization).
- Next exposure: the allergen cross-links two IgE molecules on the surface.
- Granules release histamine and tryptase within minutes: wheal, itch, bronchospasm, low blood pressure.
- Hours later, newly made leukotrienes and cytokines recruit eosinophils for the late phase.

## Markers

- FcεRI
- CD117 (KIT, mast cell)
- Tryptase
- CD123 (basophil)
- Toluidine blue (metachromatic)

## Clinical notes

- Anaphylaxis: rapid, multi-system reaction (skin, airway, circulation, gut) to foods, medicines or insect stings; a medical emergency.
- Allergic rhinitis, urticaria and allergic asthma are mast-cell driven.
- Basophilia is a clue to chronic myeloid leukemia and other myeloproliferative disorders.
- Systemic mastocytosis: clonal mast cells, often with a KIT mutation, with flushing and anaphylaxis episodes.

## In the lab

- Serum tryptase drawn soon after a suspected anaphylaxis supports the diagnosis.
- Specific IgE in blood and skin-prick tests show sensitization (not always clinical allergy).
- Basophil count in the differential.

## Memory aid

Mast cells are smoke detectors mounted in the walls and basophils are portable ones: IgE is the sensor, and when the allergen hits it the histamine alarm sounds in seconds.

## Test yourself

Think of the answer, then tap the question to see it.

## What triggers degranulation of a sensitized mast cell?

Cross-linking of IgE bound to FcεRI by a multivalent allergen.

## Which preformed mediator in the blood helps confirm anaphylaxis?

Tryptase, released from mast cell granules.

## How do mast cells and basophils differ in where they live?

Mast cells reside long-term in tissues; basophils circulate in the blood and are rare.

## A high basophil count should make one think of which blood cancer?

Chronic myeloid leukemia (and other myeloproliferative disorders).

[Add to my cards (4)](https://durgical.app/estudiar/?add=/en/immunology/mast-cell-and-basophil/)

## Related

- [Eosinophil](https://durgical.com/en/immunology/eosinophil/)
- [Type I hypersensitivity (immediate, IgE)](https://durgical.com/en/immunology/type-i-hypersensitivity/)
- [Antibody structure and isotypes (IgG, IgA, IgM, IgE, IgD)](https://durgical.com/en/immunology/antibody-structure-and-isotypes/)
- [Latex and drug allergy](https://durgical.com/en/immunology/latex-and-drug-allergy/)
- [CD markers: the table to know](https://durgical.com/en/immunology/cd-markers-the-table-to-know/)

## Related conditions

- [Anaphylaxis](https://durgical.com/en/conditions/anaphylaxis/)
- [Allergic rhinitis](https://durgical.com/en/conditions/allergic-rhinitis/)
- [Asthma](https://durgical.com/en/conditions/asthma/)

[← All of immunology](https://durgical.com/en/immunology/)

Educational content on the immune system; not a treatment or individual vaccination guide and no substitute for a health professional's advice. No doses are given.

Sources: [Mast Cells](https://www.immunology.org/public-information/bitesized-immunology/cells/mast-cells) (British Society for Immunology, 2024); [Basophils](https://www.immunology.org/public-information/bitesized-immunology/cells/basophils) (British Society for Immunology, 2024); [18.4 Leukocytes and Platelets](https://openstax.org/books/anatomy-and-physiology-2e/pages/18-4-leukocytes-and-platelets) (OpenStax, Rice University (Anatomy and Physiology 2e), 2022); [Anaphylaxis](https://medlineplus.gov/ency/article/000844.htm) (MedlinePlus, U.S. National Library of Medicine, 2024).

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Representative model, for educational purposes only.

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License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/immunology/mast-cell-and-basophil/