Before vaccination was available for common childhood diseases,
thousands of children died or were left
with permanent disabilities from
these illnesses. Unfortunately, even now, many people become ill or even die
every year from diseases that are readily prevented by vaccines.
One reason some children are not protected is that parent refuse to
have their children immunized or vaccinated, fearing the rare chance that procedure
might be harmful. Vaccines have in these cases become victims of their own
success. They have been so effective at preventing diseases that people have
been lulled into a false sense of security. Reports of adverse effects of
vaccination have led some people to falsely believe that the risk of
vaccination is greater than the risk of diseases. Although, there is some risk
associated with almost any medical procedure, there is no question that the
benefit of routine immunization outweighs the very slight risk.
Routine immunization against pertussis [whooping cough] caused by a
marked decrease in its incidence in United States and saved many adverse
reactions to the killed whole cell vaccine being used at the time however, many
parents refused to get their children vaccinated. By 1990, this refusal of
vaccination resulted in the highest incidence of pertussis cases in 20 years
and the deaths of some children, mostly those under one year of age.
The immune system, which is made
up of special cells, proteins, tissues, and organs, defends people against
germs and microorganisms every day. In most cases, the immune system does a
great job of keeping people healthy and preventing infections. But sometimes
problems with the immune system can lead to illness and infection.
WHAT IS
IMMUNE SYSTEM
The immune system is the body's defence
against infectious organisms and other invaders. Through a series of steps
called the immune response, the immune system attacks organisms and substances
that invade body systems and cause disease.
The immune system is made up of a
network of cells, tissues, and organs that work together to protect the body.
The cells involved are white blood cells, or leukocytes, which come in two
basic types that combine to seek out and destroy disease-causing organisms or
substances.
Leukocytes are produced or stored
in many locations in the body, including the thymus, spleen, and bone marrow.
For this reason, they're called the lymphoid organs. There are also clumps of
lymphoid tissue throughout the body, primarily as lymph nodes, that house the
leukocytes.
The leukocytes circulate through
the body between the organs and nodes via lymphatic vessels and blood vessels.
In this way, the immune system works in a coordinated manner to monitor the
body for germs or substances that might cause problems.
The two basic types of leukocytes
are:
1.
phagocytes, cells that chew up invading organisms
2.
lymphocytes, cells that allow the body to remember and recognize previous invaders
and help the body destroy them
A number of different cells are
considered phagocytes. The most common type is the neutrophil, which
primarily fights bacteria. If doctors are worried about a bacterial infection,
they might order a blood test to see if a patient has an increased number of
neutrophils triggered by the infection. Other types of phagocytes have their
own jobs to make sure that the body responds appropriately to a specific type
of invader.
The two kinds of lymphocytes are B
lymphocytes and T lymphocytes. Lymphocytes start out in the bone
marrow and either stay there and mature into B cells, or they leave for the
thymus gland, where they mature into T cells. B lymphocytes and T lymphocytes
have separate functions: B lymphocytes are like the body's military
intelligence system, seeking out their targets and sending defences to lock
onto them. T cells are like the soldiers, destroying the invaders that the
intelligence system has identified.
When antigens (foreign substances
that invade the body) are detected, several types of cells work together to
recognize them and respond. These cells trigger the B lymphocytes to produce
antibodies, specialized proteins that lock onto specific antigens.
Once produced, these antibodies
continue to exist in a person's body, so that if the same antigen is presented
to the immune system again, the antibodies are already there to do their job.
So if someone gets sick with a certain disease, like chickenpox, that person
typically doesn't get sick from it again.
This is also how immunizations
prevent certain diseases. An immunization introduces the body to an antigen in
a way that doesn't make someone sick, but does allow the body to produce
antibodies that will then protect the person from future attack by the germ or
substance that produces that particular disease.
Although antibodies can recognize
an antigen and lock onto it, they are not capable of destroying it without
help. That's the job of the T cells, which are part of the system that destroys
antigens that have been tagged by antibodies or cells that have been infected
or somehow changed. (Some T cells are actually called "killer
cells.") T cells also are involved in helping signal other cells (like phagocytes)
to do their jobs.
Antibodies also can neutralize
toxins (poisonous or damaging substances) produced by different organisms.
Lastly, antibodies can activate a group of proteins called complement
that are also part of the immune system. Complement assists in killing
bacteria, viruses, or infected cells.
All of these specialized cells
and parts of the immune system offer the body protection against disease. This
protection is called immunity.
IMMUNITY
Humans have three types of immunity — innate,
adaptive, and passive:
INNATE IMMUNITY
Everyone is born with innate (or natural) immunity, a
type of general protection. Many of the germs that affect other species don't
harm us. For example, the viruses that cause leukemia in cats or distemper in
dogs don't affect humans. Innate immunity works both ways because some viruses
that make humans ill — such as the virus that causes HIV/AIDS — don't make cats
or dogs sick.
Innate immunity also includes the external barriers of
the body, like the skin and mucous membranes (like those that line the nose,
throat, and gastrointestinal tract), which are the first line of defense in
preventing diseases from entering the body. If this outer defensive wall is
broken (as through a cut), the skin attempts to heal the break quickly and
special immune cells on the skin attack invading germs.
ADAPTIVE IMMUNITY
The second kind of protection is adaptive (or active)
immunity, which develops throughout our lives. Adaptive immunity involves the
lymphocytes and develops as people are exposed to diseases or immunized against
diseases through vaccination.
PASSIVE IMMUNITY
Passive immunity is "borrowed" from another
source and it lasts for a short time. For example, antibodies in a mother's
breast milk provide a baby with temporary immunity to diseases the mother has
been exposed to. This can help protect the baby against infection during the
early years of childhood.
Everyone's immune system is different. Some people
never seem to get infections, whereas others seem to be sick all the time. As
people get older, they usually become immune to more germs as the immune system
comes into contact with more and more of them. That's why adults and teens tend
to get fewer colds than kids — their bodies have learned to recognize and
immediately attack many of the viruses that cause colds.
PROBLEMS ASSOCIATED
WITH IMMUNE SYSTEM
Disorders of the immune system
fall into four main categories:
1.
Immunodeficiency disorders
(primary or acquired)
2.
Autoimmune disorders (in which
the body's own immune system attacks its own tissue as foreign matter)
3.
Allergic disorders (in which the
immune system overreacts in response to an antigen)
4.
Cancers of the immune system
IMMUNODEFICIENCY
DISORDERS
Immunodeficiencies occur when a
part of the immune system is not present or is not working properly. Sometimes
a person is born with an immunodeficiency (known as primary
immunodeficiencies), although symptoms of the disorder might not appear until
later in life. Immunodeficiencies also can be acquired through infection or
produced by drugs (these are sometimes called secondary immunodeficiencies).
Acquired (or secondary)
immunodeficiencies usually develop after someone has a disease, although they
can also be the result of malnutrition, burns, or other medical problems.
Certain medicines also can cause problems with the functioning of the immune
system.
Acquired (secondary)
immunodeficiencies include:
1
HIV (human immunodeficiency
virus) infection/AIDS (acquired immunodeficiency syndrome) is a disease that slowly and steadily destroys the immune system. It is
caused by HIV, a virus that wipes out certain types of lymphocytes called
T-helper cells. Without T-helper cells, the immune system is unable to defend
the body against normally harmless organisms, which can cause life-threatening
infections in people who have AIDS. Newborns can get HIV infection from their
mothers while in the uterus, during the birth process, or during breastfeeding.
People can get HIV infection by having unprotected sexual intercourse with an
infected person or from sharing contaminated needles for drugs, steroids, or
tattoos.
2
Immunodeficiencies caused by
medications. Some medicines suppress the
immune system. One of the drawbacks of chemotherapy treatment for cancer, for
example, is that it not only attacks cancer cells, but other fast-growing,
healthy cells, including those found in the bone marrow and other parts of the
immune system. In addition, people with autoimmune disorders or who have had
organ transplants may need to take immunosuppressant medications, which also
can reduce the immune system's ability to fight infections and can cause
secondary immunodeficiency.
AUTOIMMUNE
DISORDERS
In autoimmune disorders, the
immune system mistakenly attacks the body's healthy organs and tissues as
though they were foreign invaders. Autoimmune diseases include:
1
Lupus, a chronic disease marked by muscle and joint pain and inflammation
(the abnormal immune response also may involve attacks on the kidneys and other
organs)
2
Juvenile rheumatoid arthritis, a disease in which the body's immune system acts as though certain
body parts (such as the joints of the knee, hand, and foot) are foreign tissue
and attacks them
3
Scleroderma, a chronic autoimmune disease that can lead to inflammation and damage
of the skin, joints, and internal organs
4
Ankylosing spondylitis, a disease that involves inflammation of the spine and joints, causing
stiffness and pain
5
Juvenile dermatomyositis, a disorder marked by inflammation and damage of the skin and muscles
ALLERGIC
DISORDERS
Allergic disorders occur when the
immune system overreacts to exposure to antigens in the environment. The
substances that provoke such attacks are called allergens. The immune response
can cause symptoms such as swelling, watery eyes, and sneezing, and even a
life-threatening reaction called anaphylaxis. Medications called antihistamines
can relieve most symptoms.
Allergic disorders include:
1
1 Asthma is a
respiratory disorder that can cause breathing problems, frequently involves an
allergic response by the lungs. If the lungs are oversensitive to certain
allergens (like pollen, molds, animal dander, or dust mites), it can trigger
breathing tubes in the lungs to become narrowed, leading to reduced airflow and
making it hard for a person to breathe.
2
Eczema is an itchy rash also known as atopic dermatitis. Although atopic
dermatitis is not necessarily caused by an allergic reaction, it more often
occurs in kids and teens who have allergies, hay fever, or asthma or who have a
family history of these conditions.
3
Allergies of several types can occur in kids and teens. Environmental allergies
(to dust mites, for example), seasonal allergies (such as hay fever), drug
allergies (reactions to specific medications or drugs), food allergies (such as
to nuts), and allergies to toxins (bee stings, for example) are the common
conditions people usually refer to as allergies.
CANCERS
OF THE IMMUNE SYSTEM
Cancer occurs when cells grow out
of control. This also can happen with the cells of the immune system. Lymphoma
involves the lymphoid tissues and is one of the more common childhood cancers.
Leukemia, which involves abnormal overgrowth of leukocytes, is the most common
childhood cancer. With current medications most cases of both types of cancer
in kids and teens are curable.
Although immune system disorders
usually can't be prevented, you can help your child's immune system stay
stronger and fight illnesses by staying informed about your child's condition
and working closely with your doctor.
