PHYSIOLOGICAL ROLE OF MAST CELLS
The important cells of the immune system are known as mast cells which are the hematopoietic cells lineage. They are mainly derived from bone marrow under the impact of the c-kit ligand. Paul Ehrlich first described 130 years ago in his PhD thesis . In the bloodstream, mature mast cells do not circulate when it is under regular condition. The mast cells are normally found in epithelial tissue cells throughout the body, blood cells, smooth muscles, mucous and hair follicles . Mast cells are not found in mineralized bone, cornea and cartilage . The mast cell containing cytoplasm comprises 50 to 200 huge granules that are stored in inflammatory mediators . Outside the granules in the mast cell, the cytoplasm is lipid bodies which are the source of triglyceride-derived arachidonic acid . Mast cells cytoplasm containing few mitochondria, rough endoplasmic reticulum and many unrestricted ribosomes were observed under the electron microscope . The main mechanism of mast cells is IgE-mediated allergenic response through the FcϵRI receptor(Figure 2) . The mast cell is activated by the most common physiological pathway via IgE/antigen/ FcϵRI cross-linking pathway . FcϵRI involves α-chain that binds with IgE. IgE antibodies are produced from mature β cells in response to CD4+ Th2 cells . When β cells interact with cytokines like IL-4 the antibody class will switch from IgM to I, mostly found in FcϵRI receptors . During degranulation, the activated mast cell produces mediators such as histamine, Leukotrienes, chemokines, and cytokines. Other immune cells such as T cells, eosinophils, monocytes, neutrophils and other pro-inflammatory mediators have recruited these molecules .