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Lymph nodes are glands that play an important part in your body's defense against infection.
They produce lymph, which travels throughout your body in the lymph system, and filters
impurities from the body.
Common areas where the lymph nodes can be felt (with the fingers) include:
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Groin
Armpit
Neck (there is a chain of lymph nodes on either side of the front of the neck, both sides of
the neck, and down each side of the back of the neck)
Under the jaw and chin
Behind the ears
On the back of the head
Lymph nodes can become swollen from infection, inflammatory conditions, an abscess, or
cancer. Other causes of enlarged lymph nodes are rare. By far, the most common cause of
swollen lymph nodes is infection.
When swelling appears suddenly and is painful, it is usually caused by injury or an infection.
Enlargement that comes on gradually and painlessly may, in some cases, result from cancer or a
tumor.
Common Causes
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Infections that commonly cause swollen lymph nodes include mononucleosis, German measles
(rubella), tuberculosis, mumps, ear infection, tonsillitis, an abscessed or impacted tooth, gingivitis
(swelling of the gums), mouth sores, and sexually transmitted diseases.
Immune or autoimmune disorders that can cause swollen lymph nodes include rheumatoid
arthritis and HIV. Cancers that can cause swollen glands include leukemia, Hodgkin's disease, or
non-Hodgkin's lymphoma.
Which lymph nodes are swollen depends on the type of problem and the body parts involved.
Identifying the location can help determine the possible cause.
Swollen lymph nodes may also be caused by some medications (like phenytoin for seizures) or
certain vaccinations (namely, typhoid).
The Body's First Line of Defense
The immune system is a complex of organs--highly specialized cells and
even a circulatory system separate from blood vessels--all of which work
together to clear infection from the body.
The organs of the immune system, positioned throughout the body, are
called lymphoid organs. The word "lymph" in Greek means a pure, clear
stream--an appropriate description considering its appearance and
purpose.
Lymphatic vessels and lymph
nodes are the parts of the
special circulatory system
that carries lymph, a
transparent fluid containing
white blood cells, chiefly
lymphocytes.
Lymphatic vessels form a
circulatory system that operates in
close partnership with blood
circulation.
Lymph bathes the tissues
of the body, and the
lymphatic vessels collect
and move it eventually
back into the blood
circulation. Lymph nodes
dot the network of
lymphatic vessels and
provide meeting grounds
for the immune system
cells that defend against
invaders. The spleen, at
the upper left of the
abdomen, is also a
staging ground and a
place where immune
system cells confront
foreign microbes.
Organs and tissues of the immune system
dot the body in a protective network of
barriers to infection.
Pockets of lymphoid tissue are in many other locations throughout the
body, such as the bone marrow and thymus. Tonsils, adenoids, Peyer's
patches, and the appendix are also lymphoid tissues.
Both immune cells and foreign molecules enter the lymph nodes via
blood vessels or lymphatic vessels. All immune cells exit the lymphatic
system and eventually return to the bloodstream. Once in the
bloodstream, lymphocytes are transported to tissues throughout the
body, where they act as sentries on the lookout for foreign antigens.
How the Immune System Works
Cells that will grow into the many types of more specialized cells that
circulate throughout the immune system are produced in the bone
marrow. This nutrient-rich, spongy tissue is found in the center shafts of
certain long, flat bones of the body, such as the bones of the pelvis. The
cells most relevant for understanding vaccines are the lymphocytes,
numbering close to one trillion.
The two major classes of lymphocytes are B cells, which grow to maturity
in the bone marrow, and T cells, which mature in the thymus, high in the
chest behind the breastbone.
B cells produce antibodies that
circulate in the blood and lymph
streams and attach to foreign
antigens to mark them for
destruction by other immune
cells.
B cells are part of what is known
as antibody-mediated or
humoral immunity, so called
because the antibodies circulate
in blood and lymph, which the
ancient Greeks called, the body's
"humors."
B cells become plasma cells,
which produce antibodies
when a foreign antigen triggers
the immune response.
Certain T cells, which also patrol the blood and lymph for foreign
invaders, can do more than mark the antigens; they attack and destroy
diseased cells they recognize as foreign. T lymphocytes are responsible
for cell-mediated immunity (or cellular immunity). T cells also orchestrate,
regulate and coordinate the overall immune response. T cells depend on
unique cell surface molecules called the major histocompatibility complex
(MHC) to help them recognize antigen fragments.
Antibodies
Antibodies produced by cells of the
immune system recognize foreign
antigens and mark them for
destruction.
The antibodies that B cells
produce are basic
templates with a special
region that is highly
specific to target a given
antigen. Much like a car
coming off a production
line, the antibody's frame
remains constant, but
through chemical and
cellular messages, the
immune system selects a
green sedan, a red
convertible or a white
truck to combat this
particular invader.
However, in contrast to cars, the variety of antibodies is very large.
Different antibodies are destined for different purposes. Some coat the
foreign invaders to make them attractive to the circulating scavenger
cells, phagocytes, that will engulf an unwelcome microbe.
When some antibodies combine with antigens, they activate a cascade of
nine proteins, known as complement, that have been circulating in
inactive form in the blood. Complement forms a partnership with
antibodies, once they have reacted with antigen, to help destroy foreign
invaders and remove them from the body. Still other types of antibodies
block viruses from entering cells.
T Cells
T cells have two major roles in immune defense. Regulatory T cells are
essential for orchestrating the response of an elaborate system of
different types of immune cells.
Helper T cells, for example, also
known as CD4 positive T cells
(CD4+ T cells), alert B cells to start
making antibodies; they also can
activate other T cells and immune
system scavenger cells called
macrophages and influence which
type of antibody is produced.
Certain T cells, called CD8 positive
T cells (CD8+ T cells), can become
killer cells that attack and destroy
infected cells. The killer T cells are
also called cytotoxic T cells or CTLs
(cytotoxic lymphocytes).
Immune system process
Activation of helper T cells
T lymphocytes become
CD4+ or helper T cells, or
they can become CD8+
cells, which in turn can
become killer T cells, also
called cytotoxic T cells.
After it engulfs and processes an antigen, the macrophage displays the
antigen fragments combined with a Class II MHC protein on the
macrophage cell surface. The antigen-protein combination attracts a
helper T cell, and promotes its activation.
Activation of cytotoxic T cells
After a macrophage engulfs and processes an antigen, the macrophage
displays the antigen fragments combined with a Class I MHC protein on
the macrophage cell surface. A receptor on a circulating, resting cytotoxic
T cell recognizes the antigen-protein complex and binds to it. The binding
process and a helper T cell activate the cytotoxic T cell so that it can
attack and destroy the diseased cell.
Activation of B cells to make antibody
A B cell uses one of its receptors to bind to its matching antigen, which
the B cell engulfs and processes. The B cell then displays a piece of the
antigen, bound to a Class II MHC protein, on the cell surface. This whole
complex then binds to an activated helper T cell. This binding process
stimulates the transformation of the B cell into an antibody-secreting
plasma cell.
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Last updated September 25, 2003 (alt)
In healthy people, the spleen plays a role in immunity against bacterial infections. The spleen is
in the uppermost area of the left side of the abdomen, just under the diaphragm. It typically has
attachments to the stomach, left kidney, and colon.
If the surgery is elective (planned) rather than an emergency, your doctor will give you vaccines
against certain bacteria prior to removing the spleen. If the operation is an emergency, you
should get the vaccines after the operation.
The spleen is removed while the patient is under general anesthesia. The surgeon makes an
incision in the abdomen, locates the spleen, and separates it from its attachments to the
surrounding organs. The surgeon then divides the blood supply to the spleen and removes it
from the abdomen. After a careful check for bleeding, the abdominal incision is closed.
Some patients may be able to undergo laparoscopic surgery (also known as "keyhole" or
"telescopic" surgery) to remove the spleen. This operation is done with several tiny incisions
instead of a single large one, and recovery is typically faster. Some patients, however, are not
suited to laparoscopic surgery.
Thymus
The thymus gland lies in the upper part of the mediastinum behind the sternum and extends
upwards into the root of the neck. It weighs about 10 to 15 g.(about half an ounce) at birth and
begins to grow until the individual reaches puberty when it begins to atrophy. It’s maximum
weight is around 30 - 40g (around 1 to 1.5 ounces) by the age of 40 it has returned to it’s weight
at birth. The thymus consists of two lobes connected by areolar tissue. The lobes are enclosed in
a fibrous capsule which dips into their substance dividing them into lobules that consist of an
irregular branching framework of epithelial cells and lymphocytes.
Function
Lymphocytes originate from haemocytoblasts (stem cells) in red bone marrow. Those that enter
the thymus mature and develop into activated T-lymphocytes i.e. able to respond to antigens
encountered elsewhere in the body. They then divide into two groups :
those that enter the blood, some of which remain in circulation and some lodge in other
lymphoid tissue
those that remain in the thymus gland and are the source of future generations of Tlymphocytes.
The maturation of the thymus and other lymphoid tissue is stimulated by thymosin, a hormone
secreted by the epithelial cells that form the framework of the thymus gland. Involution of the
gland begins in adolescence and, with increasing age the effectiveness of T- lymphocyte
response to antigens declines.
Definition Return to top
Antibodies are a type of protein. They are produced by the immune system in response to
foreign substances that may be a threat to the body -- such as chemicals, virus particles, spores,
or bacterial toxins. These foreign substances are called antigens.
Each type of antibody is unique and defends the body against one specific type of antigen.
Macrophages (Greek: "big eaters") are cells found in tissues that are responsible for
phagocytosis of pathogens, dead cells and cellular debris. Macrophages are part of the innate
immune system.
Contents
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1 Origin
2 Function
o 2.1 Phagocytosis
3 Role in disease
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4 Macrophage relatives
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Origin
Macrophages are derived from monocytes. Monocytes grow in the bone marrow and enter the
bloodstream. Circulating monocytes respond to chemical mediators of inflammation. Upon
activation by these mediators, monocytes squeeze through the endothelium. Once through the
endothelium, the monocytes are called macrophages. (Some monocytes differentiate into
specialized cells such as dendritic cells or microglia).
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Function
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Phagocytosis
Their main role is the removal of pathogens and necrotic debris. The latter function is more
important in chronic inflammation. The early stages of inflammation are dominated by
neutrophil granulocytes, which are ingested by macrophages if they come of age, see CD-31 for
a description of this process.)
Macrophages also present fragments of pathogens (called antigens) that they have ingested
with MHC class II molecules on their cell membranes. Helper T cells recognize this and release a
lymphokine notification to B cells. The B cells then create and release antibodies specific to the
particular antigen, and hence to the pathogen. Macrophages again come into play because they
are especially attracted to cells with antibodies attached.
When a macrophage ingests a pathogen, the pathogen becomes trapped in a food vacuole,
which then fuses with a lysosome. Within the lysosome, enzymes and toxic oxygen compounds
digest the invader. However, some bacteria, such as Mycobacterium tuberculosis, have become
resistant to these methods of digestion.
A number of cell types are closely related to macrophages: 
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Dendritic cells (including Langerhans cells)
Microglia
Kupffer cells
Osteoclasts
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Role in disease
Due to their role in phagocytosis, macrophages are involved in many diseases of the immune
system. For example, they participate in the formation of granulomas, inflammatory lesions that
may be caused by a large number of diseases.
Some disorders, mostly rare, of ineffective phagocytosis and macrophage function have been
described.
Macrophages are the predominant cells involved in creating the progressive plaque lesions of
atherosclerosis.
When fighting influenza, macrophages are dispatched to the throat. However, until the killer T
cells for the flu virus are found, the macrophages do more damage than help. They not only
destroy throat cells infected with the flu virus, they destroy several surrounding non-infected
cells.
Macrophages also play a role in Human Immunodeficiency Virus (HIV) infection. Like T cells,
macrophages can be infected with HIV but this does not kill macrophages, and instead they act
as a reservoir of ongoing virus replication throughout the body.
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Macrophage relatives
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Tingible body macrophages are found the germinal centers of lymph nodes
Microglia occur in the nervous system
Kupffer cells are found in the liver
Dendritic cells, such as Langerhans cells of the skin, are antigen-presenting cells of the
immune system
Blood - Blood plasma
Pluripotential hemopoietic stem cell - Red blood cells (Reticulocyte, Normoblast) White blood cells
Lymphocytes (Lymphoblast)
T cells (Cytotoxic - Helper - Regulatory T cell) - B cells (Plasma cells & Memory B cells) Natural killer cell
Myelocytes (Myeloblast)
Granulocytes (Neutrophil, Eosinophil, Basophil) - Mast cell precursors - Monocytes
(Histiocyte, Macrophages, Dendritic cells, Langerhans cells, Microglia, Kupffer cells) Megakaryoblast - Megakaryocyte - Platelets
Retrieved from "http://en.wikipedia.org/wiki/Macrophage"
Category: Macrophages
gamma globulin
GAMMA GLOBULIN [gamma globulin] a group of globulin proteins in human blood plasma,
including most antibodies . These antibody substances are produced as a protective reaction of
the body's immune system to the invasion of disease-producing organisms (see immunity ).
Injections of gamma globulin are used to create a rapid but temporary immunity in patients who
have been exposed to certain diseases. Children who have been exposed to, but are not
immunized against, measles and patients with hepatitis receive some protection from gamma
globulin when it is administered during the incubation period of the infection. The gamma
globulin used for such purposes is extracted from blood plasma from a large, diverse adult
population; the resulting mixture is thus likely to contain antibodies from individuals who had
been exposed to the appropriate infections.