C H A P T E R 1 7
Immune modulators
259
response to viral invasion; and interleukins, which are
chemicals produced by T cells to communicate between
leucocytes.
I
nterferons
Interferons are substances naturally produced and
released by human cells that have been invaded by
viruses. They may also be released from cells in response
to other stimuli, such as cytotoxic T cell activity.
A number of interferons are available for use. Several
are produced by
recombinant DNA technology
, includ-
ing interferon alfa-2a (
Roferon-A
), interferon alfa-2b
(
Intron A
), peginterferon alfa-2a (
Pegasys
), peginterferon
alfa-2b (
Peg-Intron
) and interferon beta-1b (
Betaferon
).
Interferon beta-1a (
Avonex
) is produced from Chinese
hamster ovary cells. Interferon gamma-1b (
Imukin
) is
produced by
Escherichia coli
bacteria. The interferon
of choice depends on the condition being treated (see
Table 17.1).
Therapeutic actions and indications
Interferons act to prevent virus particles from replicat-
ing inside cells. They also stimulate interferon-receptor
sites on non-invaded cells to produce antiviral proteins,
which prevent viruses from entering the cell. In addition,
interferons have been found to inhibit tumour growth
and replication, to stimulate cytotoxic T-cell activity
A
s the name implies, immune modulators are used to
modify the actions of the immune system.
Immune stim-
ulants
are used to energise the immune system when it
is exhausted from fighting prolonged invasion or when
it needs help fighting a specific pathogen or cancer cell.
Immune suppressants
are used to block the normal
effects of the immune system in cases of organ trans-
plantation (in which non-self cells are transplanted into
the body and destroyed by the immune reaction) and in
autoimmune disorders (in which the body’s defences rec-
ognise self-cells as foreign and work to destroy them) in
some cancers. Each group acts at various sites within the
immune response (Figure 17.1).
The knowledge base about the actions and compo-
nents of the immune system is continually growing and
changing. As new discoveries are made and the actions
and interactions of the various components of the system
become better understood, new applications will be
found for modulating the immune system in a variety of
disorders. Box 17.1 discusses the use of immune modu-
lators across the lifespan. Box 17.2 discusses use of these
agents during pregnancy.
IMMUNE STIMULANTS
Immune stimulants (Table 17.1) include the interfer-
ons, which are naturally released from human cells in
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FIGURE 17.1
Sites of action of the immune modulators.
