Tissue Development, Repair, and Remodeling - Tissue Functioning and Remodeling in the Circulatory and Ventilatory Systems - page 722

11.5.6.10 Platelet-Activating Factor

Phospholipid platelet-activating factor provokes platelet aggregation and attracts
neutrophils. It is produced in response to stimuli by basophils, neutrophils, platelets,
and endothelial cells. It also causes bronchoconstriction and vasodilation.
Basophils sensitized with IgE degranulate release histamine and platelet-
activating factor that causes aggregation of platelets and release of their histamine
content [ 1467 ].

11.5.6.11 TRAF2 and Sphingosine 1-Phosphate

Tumor-necrosis factor receptor (TNFR)-associated factor TRAF2 participates in
signaling by the classical inflammatory cytokine TNF

. Sphingosine 1-phosphate is
a cofactor for TRAF2 ubiquitin ligase. It binds to TRAF2 and promotes polyubiqui-
tination of receptor-interacting protein kinase RIPK1 by TRAF2 downstream from
TNFR and Toll-like receptors [ 1468 ]. Kinase RIPK1 then activates the I

α

κ Bkinase

complex and consequently nuclear factor- κ B.

11.5.6.12 Complement System

Acute-phase proteins trigger formation of the membrane attack complex and release
of complement components, such as fragment C3b of complement component-3. 51
Phagocytosis also leads to the production of inflammation mediators, like NO,
peroxides, and oxygen radicals, which are toxic to invading microorganisms.
Fibroblasts form connective tissue.

11.5.6.13 Inflammasome and Caspases

Inflammasome, a cytosolic protein complex, is made of precursors of pro

β

-inflammatory caspases. These caspases cleave the precursor of interleukin-1 .Ac-

β

tive IL1 causes a potent inflammatory response. Inflammasome contains NALP1,

51 The complement system is an important component of innate immunity. Activation of the
complement system produces derived products that contribute to pathogen elimination; but
inappropriate stimulation of the complement system leads to inflammatory diseases. Complement
component-3 (C3), once activated, forms fragments. The C3b fragment cements the assembly of
convertases for C3 and C5 activation. C3 cleavage and activation of C3 allows binding with various
molecules. The proteolysis of C3b gives birth to other fragments, such as C3c.