Cytokines with clearly defined actions in acute inflammation and early tissue injury include which of the following?
A. Cysteine-X-amino acid Cysteine (CXC) chemokinesB. Tumor Necrosis Factor (TNF α)
C. Transforming Growth Factor-beta
D. Interleukin-1
E. Platelet Derived Growth Factor
The Answer
is.: B. Tumor Necrosis Factor (TNF α) , D. Interleukin-1
Polypeptide mediators, such as TNFa and IL-1, are
considered “early response” cytokines and are actively involved in the
initiation of the cascade of events which precipitate acute inflammation. In
addition to being important triggers for the induction of other cytokines
important inflammatory network, TNFa and IL-1 appear to be key mediators in
promoting the adherence of inflammatory cells to the endothelium. IL-i is a
complex, multifunctional molecule that shares many overlapping biological
properties with TNFa. In addition, both IL-i and TNFa potentiate the effects of
one another. The most important function of 1L-1 appears to be the regulation
of the hepatic acute phase response. Following injury, a number of physiologic
changes develop within several hours. IL-1 is one of the primary stimuli for
the production of acute phase proteins from the liver. Endotoxin, IL-1, TNFa
and PDGF are capable of causing significant induction of IL-6 synthesis.
Over the last decade, at least 12 different C-X-C
chemokines have been identified. These include IL-8, one of the most potent
mediators of chemotaxis known. TNFa and IL-i are key molecules for the
induction of IL-8, which in turn is important for the induction of neutrophil
recruitment and activation. Similar properties are apparent for other members
of this chemokine family.
Platelet activation and degranulation occur during
coagulation following injury, leading to the deposition of a number of cytokines
into the provisional matrix. These cytokines include transforming growth
factor-a, (TGFa), transforming growth factor 3 (TGF-3), platelet- derived
growth factor (PDGF), and neutrophil activating peptide-2 (NAP-2). These
cytokines are either important growth factors or chemotaxis for leukocytes,
endotheIial cells, fibroblasts, and keratinocytes which are key components in
the process of tissue repair. Thus, coagulation and platelet activation provide
the initial foundation for subsequent cellular recruitment.
