Blood Cells - Tissue Functioning and Remodeling in the Circulatory and Ventilatory Systems - page 101

Table 3.14. Molecules of mastocytes (Source: [ 194 ]). ( Part 1 ) Granule-stored preformed me-
diators and de novo synthesized mediators. Mastocytes interact with blood vessels and nerves.
The set of expressed cytokines varies according to the maturity state of mastocyte and tissue of
residence. Histamine, eicosanoids, and other effectors are released upon crosslinking of surface-
bound immunoglobulin-E by allergens or other mediators, such as T H2 -cell cytokines (IL3,
IL5, and IL13), fibroblast growth factor-2, transforming growth factor- , and proteoglycans.

Other stimuli that provokes the release of mastocyte mediators comprise C3a to C5a, UV light,
substance-P, bacterial products,

β

-melanocyte-stimulating hormone released by keratinocytes,
IL8, etc. Stem cell factor in the skin, produced by keratinocytes, endothelial cells, fibroblasts,
melanocytes, and mastocytes, stimulates melanocytes and mastocytes (autocrine regulation) via
SCFR receptor. Lipid mediators (cyclooxygenase [prostaglandins] and lipoxygenase [leukotrienes]
metabolites of arachidonic acid) improve innate responses by recruiting pro-inflammatory cells.
Mastocytes are sources of coagulation-regulating factors. Mastocytes store several peptidases in
their secretory granules (tryptase, chymase, carboxypeptidase-A, and cathepsin-G). Chymase can
activate collagenase and stromelysin, destruct vitronectin and fibronectin, and elicit fibroblast
proliferation.

α

Agent Effects

Granule-stored preformed mediators

Histamine Allergy, inflammation

Vasodilation
Increase in blood flow and vessel wall permeability
Upregulation of endothelium adhesion molecules
Upregulation of keratinocyte expression of integrins
Fibroblast proliferation

Serotonin Vasoconstriction during injury

Endothelial nitric oxide synthase activation

Proteoglycans Clotting control

(mainly heparin)
Peptidases Proteolysis

Activation of matrix metallopeptidases
(MMP2 and MMP9 by chymase)

De novo synthesized mediators

Prostaglandin-D2 Nervous regulation

Leukotriene-B4 T-cell recruitment

Leukotriene-C4 Allergen-mediated release (no bacterial priming)

Leukotriene-B4/C4/D4 Keratinocyte growth

Platelet-activating factor Moncyte/macrophage recruitment and activation

3.8.3.2 Skin Mastocytes

Mastocytes in the skin exhibit a distribution gradient. The smaller the distance to
epidermis, the denser the population. Skin mastocytes at the vanguard of the body's
defense display multiple receptors and secrete numerous products (Table 3.17 ).