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Mast Cell is an immune cell that plays an important role in the inflammatory responses of the immune system. They are present throughout the human body but are especially concentrated near blood vessels and in the respiratory tract. Mast cells are named after their ability to release protein-antibody complexes known as "mast cell granules" on detecting something potentially harmful to the body. Mast cells also have ‘heparin’, which allows them to form other cells, including neutrophils and platelets. This allows mast cells to perform many essential functions, such as preventing microbes from entering tissue spaces and regulating inflammatory responses during any injury or infection.
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Key Terms: Mast Cells, White Blood Cells, Tissues, Immune System, Inflammation, Epithelial Tissues, Mediators, Degranulation
What is Mast Cell?
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Mast Cell is a type of white blood cell that is found in tissue and organs.
- Mast Cells are involved in allergic reactions, inflammatory responses, and other purposes.
- Mast cells are not single cells but rather white blood cells, and they are found in different tissues and organs as well as outside the body.
- Mast cell biology in rodents has been divided into two categories, namely connective tissue and mucosal mast cells.
Mast Cell
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| Immunity | Antihistamine | Leucocytes |
Location of Mast Cells
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Mast cells are found in mucosal and epithelial tissues all over the body.
- In rodents, mast cells also reside in the peritoneal and thoracic cavities.
- Mast cells can be found in all vascularized tissues except for the central nervous system and the retina.
- Although mast cells are found at the interface of the host and the external environment at antigen entry points, they are also located below the epithelium in connective tissue covered with white blood cells.
Mast Cell Activation and Degranulation
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Mast cells are censorious and participate in the inflammatory process.
- Once they get activated, mast cells secrete mediators or compounds that may cause inflammation through storage granules. or quickly delving deeper into the local microenvironment.
- Mast cells are inactive during allergic reactions until an allergen attaches to lgE, which has already been coated on the cell.
- Some membrane activation events may prepare mast cells for degranulation.
- Mast cells have a very high affinity for the Ig and Fe regions, which are the least present in the antibodies.
- Mast cells become surrounded by lgE, which is formed by plasma cells; it is a cell that produces antibodies for the immune system.
Role of Mast Cells in Inflammation
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Mast cells play a major role in inflammation by releasing histamine, which has several varieties and effects on the body, from smooth muscle contraction to vasodilation.
- Mast cells work as immune sentinel cells to respond directly to pathogens.
- They send signals to other tissues to modulate both innate and adaptive immune responses.
- Increasing corroboration implicates mast cells in inflammatory diseases.
- Here they are started by non-allergic triggers, such as neuropeptides and cytokines, often exerting synergistic results as in the case of IL-33.
- Mast cells can also release pro-inflammatory mediators selectively without degranulation.
Mast Cell Mediators
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Mast cell mediators are the ability of the mast cell to function in both a healthy state and a disease. It is dependent on not only the relevant abundance of mast cells in tissue but also on the nature and extent of mediators released.
- They are dictated by the threshold and magnitude of the mast cell.
- Mast cells can reduce a multitude of pro-inflammatory mediators.
- Degranulation is the quick response of mast cell activation to an appropriate stimulus.
- Mast cell granules are significantly rich in proteases.
- These proteases are the main proteins present in mast cells.
Several mediators are secreted into the covered environment:
- Serine Proteases, including tryptase and chymase.
- Serotonin
- Adenosine Triphosphate
- Lysosomal Enzymes
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| Antigen and Immunology | Glycosaminoglycans | Respiratory System Disorders |
| Lymphocyte | Bone Marrow | Difference Between RBC and WBC |
Mast Cells and Immune System
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Mast cells and the immune system are both intimately connected.
- Mast cells are a type of white blood cell that releases chemicals called mediators to help us fight off foreign invaders.
- Mast cells can accelerate the onset and severity of inflammation, tissue remodeling, and, in some cases, tissue injury associated with immune responses.
- They can give rise to innate or modifying immune responses to pathogens, as well as allergic or autoimmune disorders.
- Mast cells play a major role in how the immune system reacts to certain bacteria and parasites, and they also help control other types of immune responses.
- They contain chemicals such as histamine, heparin, cytokines, and growth factors.
Things to Remember
- Mast Cells are cells involved in allergic reactions and inflammatory responses in the immune system.
- They are most commonly found in blood vessels and the respiratory tract.
- Mast cells can be found in all vascularized tissues except for the central nervous system and the retina.
- They are inactive during allergic reactions until an allergen attaches to lgE.
- Stimulation of mast cells releases mediators through storage granules.
- Mast cells are known to secrete large amounts of protein-rich material and the enzyme peptidase.
Previous Years’ Questions
- Mast cells are associated with…
- Mast cells of connective tissue contain… (AIPMT 2004)
- Mucus-secreting cells of epithelium tissue are called… (MP PMT 2012)
- Histamine is secreted by… (JIPMER 2018)
- Which of the following cells of connective tissue secrete antibodies… (UP CPMT 2005)
- Heparin is secreted by… (JIPMER 2005)
- Histamine-secreting cells are found in… (NEET 1989)
- Pepsinogen is secreted by… (Delhi UMET/DPMT 2007)
- The antibody produced in an allergic reaction is… (UPSEE 2018)
- Use of anti-histamines and steroids give quick relief… (NEET 2009)
Sample Questions
Ques. What is a mast cell? (2 Marks)
Ans. Mast cells are a type of white blood cell that is found in tissue and organs. Mast cells are also immune cells that help the immune system protect the body from diseases and allergies. They can be seen throughout the body but are especially concentrated near blood vessels and in the respiratory tract.
Ques. Where are mast cells found? (2 Marks)
Ans. Mast cells are produced in the bone marrow, which is a spongy tissue found in the hollow centers of some bones. Bone marrow tends to live longer than normal cells. They play an important part in the immune system and help to fight infections.
Ques. What is the role of mast cells in inflammation? (2 Marks)
Ans. Mast cells are the key to the inflammatory process. They can be activated to release a wide variety of inflammatory mediators with the help of different antigens that include allergens, pathogens, and physiological mediators.
Ques. What is the function of mast cells? (3 Marks)
Ans. Mast cells play an important role in allergic reactions and increase immunity against parasites. It produces histamines and other chemical mediators that promote allergic reactions. Mast cells also function in chronic airway inflammatory response, remodeling, and symptomology.
Mast cells also function during wound healing. Mast cells play a key role in physiological processes such as tissue repair and wound healing. Mast cells are widely accepted as having a crucial role in innate and adaptive immunity.
Ques. Are mast cells and basophils the same? (2 Marks)
Ans. Mast cells are very similar to the basophil in both appearance and function, Basophil is another type of white blood cell. Though mast cells were once thought to be tissue-resident basophils, it is now made clear that the two cells develop from different hematopoietic lineages and thus cannot be the same cells.
Ques. What are mast cell mediators? (3 Marks)
Ans. A unique, stimulus-specific set of mast cell mediators is released through degranulation which is followed by the activation of cell surface receptors on mast cells. Some examples of mediators that are released into the extracellular environment during mast cell degranulation are as follows:
- Serine Proteases like Tryptase and Chymase
- Histamine
- Serotonin
- Proteoglycans
- Adenosine Triphosphate (ATP)
Ques. Explain the function of mast cells in the nervous system. (3 Marks)
Ans. Mast cells naturally occur in the human brain where they interact with the neuroimmune system. Mast cells are located in a number of structures in the brain that mediate visceral sensory or neuroendocrine functions.
They serve the same general functions in the body and central nervous systems, such as affecting or regulating allergic responses, innate and adaptive immunity, autoimmunity, and inflammation. Mast cells also serve as the main effector cell through which pathogens can affect the gut-brain axis.
Ques. What are mast cell activation disorders? (3 Marks)
Ans. Mast cell activation disorders (MCAD) are defined as a spectrum of immune disorders. These disorders are unrelated to pathogenic infection and involve similar symptoms that arise from secreted mast cell intermediates. However, they do differ slightly in their pathophysiology, treatment approach, and distinguishing symptoms. Some of the mast cell activation disorders are as follows:
- Allergic Disease
- Anaphylaxis
- Neoplastic Disorders
- Mast Cell Activation Syndrome
Ques. What is the response of mast cells in the respiratory tract? (3 Marks)
Ans. Mast cells can be found throughout the lining of the respiratory tracts. In response to an antigen, mast cells will trigger an immune response which would include:
- Constriction of Airways
- Increased Production of Mucus
- Congestion
- Coughing
Ques. Do mast cells play any role in gastrointestinal diseases? (3 Marks)
Ans. Since mast cells line the intestinal tract, they have been implicated in playing a role in the following two gastrointestinal diseases:
- Food Allergy
- Irritable Bowel Syndrome
The effects of mast cells in these two diseases can be seen as
- Fast Transit of Stool which leads to Diarrhea.
- Increased fluid secretion in the large intestine which also contributes to diarrhea.
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