Mast cells are immune system cells that primarily reside in tissues rather than blood, playing a crucial role in the body's first response to external antigens. They originate from bone marrow and release various inflammatory mediators and pro-angiogenic factors essential for immune defense and maintaining homeostasis, particularly in the gastrointestinal tract. Mast cells also contribute to both innate and adaptive immunity, but their over-activation can lead to allergic reactions.

1. MAST CELLS
IMMUNOLOGY
EIMMY DENNISSE CONTRERAS

2. Mast cells are cells of the
immune system of the
hematopoietic lineage that
remain widely distributed in
vascularized tissues throughout
the body.
Mast cells are thus considered
one of the first cells of the
immune system that interact
with external antigens.

3. • Mast cells, unlike other immune cells, do not remain
in the blood but remain localized in mucosal and
epithelial tissues throughout the body.
• Primarily involved in the IgE-dependent responses.
• These are produced from the bone marrow and are
released into the blood as undifferentiated cells.
These cells then mature after they leave the blood
and reach the specialized tissues.
• In the bone marrow, mast cells originate from
CD34+/CD117+ pluripotent progenitor cells, and the
maturation of these cells depends on KIT activation.

4. • Mast cells secrete different pro-angiogenic factors like
VEGF, bFGF, TGF-beta, and IL-8.
• The cells also release proteases and heparin, which
induce permeability of the microvasculature, inducing
angiogenesis. Mast cells are among the first line of
defense against antigens entering the body. These cells
are thus important for maintaining the homeostasis of the
body, especially the gastrointestinal tract.
• In innate immunity, receptors on mast cells bind to
antigens, causing a release of inflammatory mediators like
IL-4, TNFα, and IL-6.
FUNCTIONS

5. • These cells also help in providing immunity against viral
antigens by the release of IFN-α and IFN-β.
• In adaptive immunity, mast cells process and present
antigen via MHCI and MHCII, and these also activate
dendritic cells, which are professional antigen-presenting
cells.
• The most important and prominent function of mast cells
is the release of newly synthesized mediators necessary
for the immune response.
• Mast cells are also involved in an allergic reaction where
the over-activation of mast cells can result in hyper-
allergic reactions.
FUNCTIONS