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Basophils/Mast
Cells:
Mast cells are found principally in perivascular sites
in tissues, whereas basophils are rare, circulating granulocytes.
Basophils and Mast cells are very closely related functionally
and have many similarities, such as a cytoplasm loaded with coarse granules.
Both mast cells and basophils have high affinity receptors
for the Fc portion of IgE. An explosive degranulation with release of
histamine and other potent inflammatory mediators occurs when these cells
are appropriately stimulated - for example when antigen binds IgE that
is bound to the mast cell/basophil.
Mast cells are major cellular sources of histamine,
which is so important to the initial vascular phenomenon of acute inflammation.
Mast cells are found throughout tissues in virtually
every organ of the body. They are "born" in the bone marrow,
circulate in the blood as undifferentiated and unrecognizable cells, and
they migrate into tissues where they differentiate and become histologically
recognizable. They are most numerous at sites of "contact" with
the external environment, such as skin, respiratory tract and gastrointestinal
tract. Mast cells are most numerous around small blood vessels, which
fits well with their function as inducers of vascular permeability.
Immunological, inflammatory and allergic stimuli activate
mast cells and basophils and produce degranulation with mediator release.
These cells are intimately involved in the pathogenesis of acute inflammation
because it is their release of histamine that triggers many of the immediate
clinical manifestations arising from smooth muscle contraction and increased
vascular permeability.
 
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