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The mast cell

Its significant role in immunity

The mast cell


The mast cell is the first white blood cell to respond to infection or injury, they are located in many connective tissues throughout the body, especially in areas that introduce foreign bodies such as the gastrointestinal tract, respiratory epithelium and the skin. Mast cells are a crucial part in adaptive and innate immunity, in response to pathogens, allergens and toxin exposure they release chemicals and recruit other immune cells.


They are created from pluripotent progenitor cells of myeloid lineages; these cells differentiate due to exposure and influence of stem cell factors. There are two types of mast cells in the human body, the first is called TC mast cells and contains tryptase, proteases and chymotryptic proteinase, the second is know as a T mast cell which contains only tryptase. The two types of mast cells are mucosal and connective tissue mast cells, mucosal mast cell are found mostly in the respiratory tract and the gut.


Mast cells are found in three forms, granulated, spreading and intact. Intact mast cells lay in the epithelial tissue, the less common spreading mast cells are found in the connective tissues, and granulated mast cells are those which have released their mediators. These mediators reside in the cytoplasm of the mast cell, these include tryptases, heparin, histamine, cytokines, chymase, leukotrienes, TNF- alpha and many more. Mast cells are coated in IgE antibodies that crosslink (bind) to allergen proteins, which ultimately triggers degranulation.


Mast cell disorders


Abnormal growth of mast cells leads to a variety of issues, mast cell activation syndrome in its primary state is caused by mast cell clone overproduction resulting in mastocytosis. This can lead to hives, gastric symptoms, and anaphylaxis. In some cases aggressive mastocytosis can lead to death. Cutaneous mastocytosis cause redden lesions of the skin and is most common in infants, systemic mastocytosis is most common in adults, led by the accumulation of mast cells in the intestines, organs, and bone marrow. Systemic mastocytosis includes the rare leukaemia and sarcoma forms.


Mast cell activation syndrome is its secondary state is in an IgE -mediated hypersensitive response to external factors, that contribute to the release of pro-inflammatory cytokines and increase blood flow. However, it is too abundant, the mast cells trigger far more granulation than that which is required. Idopathic mast cell activation is severe responses to the exposure of pathogens, toxins and other triggers. In idiopathic mast cell activation may patients can develop anaphylactic allergic reactions, this can present as difficulty breathing, selling and hives.


Conclusion


Mast cells play a crucial role in biological defence and are derived from stem cells in the bone marrow. They come in different forms and locations delivering an efficient response to injury and infection. When unregulated they can lead to the development of disorders ranging from mild rashes to severe anaphylaxis.

 


By Lauren Kelly

 

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