Cytokines: Interleukins
137
Tab. 5
(
continued
)
Interleukin
Principal activities
IL-14
– Inducer of proliferation of activated B cells (but not resting B cells).
– Inhibits Ig secretion by mitogen-stimulated B cells.
IL-15
– Inducer of proliferation of T cells and T-cell lines.
– Activates NK and LAK cells.
IL-16
– Lymphocyte chemoattractant factor; stimulates migratory response in CD4
+
lymphocytes, monocytes and eosinophils.
IL-17
– Induces IL-6 and IL-8 production in Fbroblasts; neutrophil recruitment.
– Enhances cell surface antigen and adhesion molecule expression.
IL-18
– Induces T-cell I±N
γ
production in combination with IL-12.
– Enhances T-cell cytotoxicity and inflammatory responses.
IL-19
– S
imi
lartoIL-10,butpoor
lydeFnedasyet.
IL-20
– Involved in skin differentiation and keratin expression.
IL-21
– Regulation of NK cell activation and differentiation.
IL-22
– Activates synthesis of acute-phase proteins in liver cells.
IL-23
– S
imi
lartoIL-12,butpoor
lydeFnedasyet.
IL-24
– Induction of apoptosis and inhibition of proliferation in tumor cells.
IL-25
– Induces expression of Th2 type immunosuppressive interleukins.
IL-26
– Not known.
IL-27
– S
imi
lartoIL-12,butpoor
lydeFnedasyet.
IL-28/29
– Induce antiviral activity.
(GEMM-CFU) and in the stimulation of
erythroid burst-forming units (BFU-E) and
megakaryocyte progenitors. There is some
evidence that IL-3 also acts on very early
multipotential progenitor cells. IL-3 may
be considered to act as a progression factor
following cell activation with competence
factors, such as IL-1. IL-3 may also stim-
ulate the proliferation/differentiation of
more mature cells of the myeloid lineage,
for example, by inducing macrophage pre-
cursors to express cytokine receptors, such
as M-CSF-R. There is experimental data
showing that IL-3 has a growth-supporting
activity for murine mast cells, but it is not
clear that this is so for human mast cells.
In
vivo
,
release
of
IL-3
by
injected
WEHI-3B
tumor
cells
results
in
the
stimulation of all of the various types
of hematopoietic cells predicted from the
in vitro
investigations, that is, increases
in numbers of myeloid cells, erythroid
cells,
mast
cells,
and
megakaryocytes.
Administration of IL-3 to mice, primates,
and humans yields broadly similar effects;
the progenitors of mast cells, neutrophils,
and macrophages are increased.
4.4
Interleukin-4
IL-4 was originally discovered by its action
on B lymphocytes and was the ±rst B-
cell stimulating factor (BSF-1, Table 1) to
be characterized. B lymphocytes, which
express surface Ig, were found only to
proliferate in response to anti-Ig if IL-
4 (BSF-1) was present. It would appear
that IL-4 is a B-lymphocyte competence
factor,
perhaps
the
counterpart
of
IL-
1
for
T
lymphocytes.
As
such,
IL-4
is involved in B-lymphocyte activation,
rather
than
proliferation,
resulting
in,
for example, the increased expression of
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