The interleukins represent another large family of cytokines, with at least 25 different constituent members having been characterized thus far. Most of the interleukins are produced by a number of different cell types. Here, we introduce one of the important interleukins, interleukin-2. Contents contain interleukin-2 receptor, biological activity, cancer treatment, infectious diseases and Inhibition of interleukin-2 activity.
2. Interleukin-2, also known as T cell growth factor, represents the most studied
member of the interleukin family. It was the first T cell growth factor to be
identified and it plays a central role in the immune response. It is produced
exclusively by T lymphocytes (especially T helper cells), in response to activation
by antigen and mitogens.
Human Interleukin-2 is a single chain polypeptide containing 133 amino acids. It
is a glycoprotein, the carbohydrate component being attached via an O-linked
glycosidic bond to threonine residue No. 3. The mature molecule displays a
molecular mass ranging from 15–20kDa, depending upon the extent of
glycosylation. The carbohydrate moiety is not required for biological activity.
3. Interleukin-2 induces its characteristic biological activities by binding a specific
receptor on the surface of sensitive cells. The high-affinity receptor complex
consists of three membrane-spanning polypeptide chains (α-, β- and γ-). The α-
chain binds Interleukin-2 with low affinity, with binding being characterized by
high subsequent association–disassociation rates. The γ-subunit does not
interact directly with Interleukin-2. It is sometimes known as γc (common) as it
also appears to be a constituent of the IL-4, -7, -9, -13 and -15 receptors.
Summary of the polypeptide constituents of the high-affinity human IL-2 receptor
4. Biological
Activity
Act as a critical autocrine growth factor for T cells,
and the magnitude of the T cell response is
largely dependent upon the level of IL-2
produced.
Serve as a growth factor for activated B
lymphocytes
Stimulate enhanced antibody
production and secretion
Promotes further differentiation of NK cells,
forming lymphokine-activated killer cells (LAKs)
Promote the growth of natural killer (NK)
cells.
5. Transformed cells expressing tumour-specific
surface antigens, which closely resemble
normal surface antigens, may not induce an
immune response.
Most transformed cells do not express class II
MHC molecules and express lower than normal
levels of class I MHC molecules.
Some tumours secrete significant quantities of
cytokines and additional regulatory molecules
which can suppress local immunological activity
Antibody binding to many tumour antigens
triggers the immediate loss of the antibody–
antigen complex from the transformed cell
surface by either endocytosis or extracellular
shedding.
The glycocalyx can possibly shield tumour
antigens from the immune system
Cancer
TreatmentTS
The immunostimulatory activity of
IL-2 has proved beneficial in the
treatment of some cancer types.
There exists direct evidence that
the immune system mounts an
immune response against most
cancer types.
The exact molecular details of how
such 'tumour escape' is achieved
remains to be conformed, although
several mechanisms have been
implicated, including
6. Infectious Diseases
Some such agents have even evolved to survive and
replicate within macrophages subsequent to uptake
via phagocytosis. This is often achieved on the basis
that the phagocytosed microbe is somehow capable
of preventing fusion of the phagocytosed vesicle with
lysozomes. Examples of pathogens capable of survival
within macrophages include:
Mycobacteria
Listeria
monocytogenes
Legionella
pneumophila
8. Inhibition of
IL-2 activity
Administration of soluble forms of the IL-2 receptor,
which would complete with the native (cell surface)
receptor for binding of IL-2
Administration of monoclonal antibodies
capable of binding the IL-2 receptor
Administration of IL-2 variants which retains
their ability to bind the receptor but fail to
initiate signal transduction
administration of IL-2 coupled
to bacterial or other toxins
9. Address: 45-16 Ramsey Road, Shirley, NY 11967, USA
Email: info@creative-peptides.com
THANKS
