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interleukin-13 (IL13) 410 interleukin-14 (IL14)
Interleukin-13.
Ribbon diagram of IL-13 that constitutes a theoretical model of human
IL-13. This is the first of two alternative structures of IL-13 generated by
homology modeling.
interleukin-13 (IL13)
A cytokine synthesized by numerous cell types, especially
T helper type 2 (Th2) cells. A significant mediator
of allergic inflammation and disease. It exerts effects on
immune cells that resemble those of the closely related
IL4 cytokine. It is a central mediator of allergic inflammation
in numerous tissues. It induces its effects through
a multisubunit receptor that includes the α chain of the
IL4 receptor (IL4Rα) that is also a constituent of the
IL4 receptor and one of two known IL13-specific binding
chains. IL13’s biological effects are associated with a
single transcription factor, signal transducer and activator
of transcription 6 (STAT6). The functions of IL13 resemble
those of IL4, especially with respect to changes induced
on hematopoietic cells. IL13 can induce IgE secretion
from activated human B cells. It acts as a molecular bridge
linking allergic inflammatory cells to nonimmune cells in
contact with them, thereby altering physiologic function. In
addition to its role in the induction of airway disease, IL13
also has anti-inflammatory properties. The protein degrading
enzymes known as airway matrix metalloproteinases
(MMPs) are requisite to induce egression of effete parenchymal
inflammatory cells into the airway lumen where
they are cleared. IL13 induces these MMPs as a mechanism
to protect against excessive allergic inflammation that
may lead to asphyxiation. IL13 facilitates the expulsion
of offending organisms or their products from parasitized
organs. Expulsion of helminths from the mouse gut
required IL13 secreted by Th2 cells. The cytokine fosters
an environment hostile to the parasite, including enhanced
contractions and glycoprotein hypersecretion from gut
epithelial cells, leading ultimately to detachment of the
organism from the gut wall and its removal. Schistosoma
mansoni eggs may lodge in various organs and tissues
including the gut wall, liver, lung, and central nervous system,
leading to the formation of granulomas with the control
of IL13. This leads ultimately to organ injury and often
significant or fatal disease, not resolution of the infection.
IL13 may antagonize Th1 responses required for resolution
of intracellular infections, leading to recruitment of aberrantly
large numbers of Th2 cells. IL13 inhibits the ability
of host immune cells to destroy intracellular pathogens. It
mediates many features of allergic lung disease including
airway hyperresponsiveness, goblet cell metaplasia, and
mucus hypersecretion, all of which contribute to airway
obstruction. IL4 also contributes to these changes but is less
significant than IL13 in that regard. IL13 induces secretion
of chemokines needed for recruitment of allergic effector
cells to the lung. STAT6 transgenic mouse investigations
reveal the possibility that IL13 signaling occurring only
through the airway epithelium is requisite for most of these
effects. The high affinity IL13 receptor complex consists of
the IL4Rα chain and an IL13-binding protein designated
the IL13Rα chain. The IL13 receptor is expressed on B
cells, monocytes/macrophages, basophils, mast cells, and
endothelial cells but not on T cells. The IL13R complex
also acts as a second receptor for IL4. The IL13Rα chain is
a specific binding protein for IL13. IL4 can signal through
both IL13R and IL4R complexes. Both IL4 and IL13 can
mediate their biological actions through the IL13R complex.
interleukin-14 (IL14)
Formerly known as high molecular-weight B cell growth
factor (HMW-BCGF), IL14 is a cytokine produced by follicular
dendritic cells, germinal center T cells, and some
malignant B cells. Normal and malignant B cells, notably
germinal center B cells and NHL-B cells, respectively,
express receptors for IL14. Its predominant activity is to
enhance the proliferation of B cells and induce memory B
cell production and maintenance. It also inhibits antibody
secretion. It is synthesized principally by T cells and
selected malignant B cells. Work with NHL-B cell lines
has shown that inhibition of the expression of the IL14 gene
results in diminished cell growth and eventual cell death.
Also called taxilin. Two distinct transcripts produced from
opposite strands of the il14 locus gene are called IL14α and