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 .