The Goldilocks Phenomenom

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The Goldilocks Phenomenom Powered By Docstoc
					The Goldilocks phenomenon

Disorders in an individual’s immune system can result in conditions of varying severity from affecting
quality of life through to death. Often described as the “Goldilocks phenomenon”, the activity of the
immune system can result in disorders through either not reacting readily enough or by eliciting an
immune response too promptly. In the first instance, where the immune system is not responsive enough,
immunodeficiency diseases can occur, often resulting in recurring and life-t hreatening infections

Immunodeficiency can arise from a number of sources; the result of a genetic disease, such as in the
case of severe combined immunodeficiency (SCID); from the use of pharmaceuticals, such as
immunos uppressive drugs; or through an infection, such as acquired immune deficiency syndrome (AIDS)
that is caused by the retrovirus HIV. In situations when the immune system is hyperactive and works
more effectively than it should, the result can be an attack on normal tissues, as if they were foreign
organisms. This can result in autoimmune diseas es such as diabetes mellitus (type I diabetes),
rheumatoid arthritis, lupus erythematosus, coeliac disease and allergies to name but a few.


Immunodeficiency can occur when one or more components of the immune system are defective or
inactive. The ability of the immune system to respond to pathogens is reduced in both the very young and
the elderly, with immune responses starting to decline a fter the age of 50 on average due to
immunos enescence. In developed countries obesity, alcohol consumption and drug abuse are common
causes of poor immune function. However, malnutrition is the most common cause of immunodeficiency
globally due to the often poor diet of individuals in developing countries. Diets lacking sufficient protein
and deficiency of single nutrients such as iron, copper, zinc, selenium, vitamins A, C, E, and B6, and folic
acid have all been report ed to reduce immune responses. Additionally, loss of thymus function at an early
age through genetic mutation or surgical removal, for example during some paediatric heart surgery, can
result in severe immunodeficiency. Immunodeficiency can also be inherited, for example chronic
granulomatous disease (CGD) is a genetic condition whereby patients suffer from recurrent bouts of
infection due to the decreased capacity of their immune system’s phagocytes to fight off diseas e -causing
pathogens. HIV infection and some types of cancer result in acquired immunodeficiency as a symptom.

Overactive immune res ponses

In contrast, an overactive immune system can be the cause of several conditions characterised by an
inappropriate res ponse by the immune system. This can be down to either a failure to fully distinguish
between self and non-self, thus resulting in an attack on the body 's own tissues as in the case of
autoimmunity, or by an over-reaction to the environment in the instance of hypersensitivity. These
undesirable and damaging responses may be divided into four classes based on the mechanisms
involved and the timeframe of the reaction

Immunodeficiency case study

Severe combined immunodeficiency (SCID), or Boy in the Bubble Syndrome, is a severe, genetically
inherited immunodeficiency disorder in which one’s adaptive immune system is completely disabled due
to a defect in one of several genes. SCID is listed as a rare disease by the Office of Rare Diseases of the
National Institutes of Health, meaning that SCID, or a subtype of SCID, affects less than 200 000 people
in the US population. Affected individuals are extremely vulnerable to infectious diseases with symptoms
including chronic diarrhoea, ear infections, recurrent pneumonia and profuse oral infection with Candida.
Babies born with SCID, if untreated, usually die within their first year due to severe, recurrent infections.
Several US states are undergoing pilot studies to diagnose SCID in newborns (as of February 1st 2009
Wisconsin and Massachusetts screen all newborns). To date, the most comm on treatment for SCID is a
bone marrow transplant from a related donor, preferably in the first 3 months after birth or before the child
is born. Gene therapy techniques have also been developed and as a res ult, the first treatment of SCID
patients occurred in 2000 and allowed these individuals to have a functional immune system for the first
time. These trials are, however, on hold due to an increased occurrence of leuk emia in these patients.
Hypersensitivity case study

Asthma is a very common chronic disease the affects the respiratory system whereby the airways
constrict, become inflamed and lined with excess mucus. Often in response to one or more triggers, an
asthmatic response may result from ex posure to airborne allergens, tobacco smoke, cold or wa rm air,
perfume, exercise, stress to name but a few. Symptoms of asthma can range from mild to life-threat ening
and include wheezing, chest tightness and itching, coughing and shortness of breath. Such symptoms
can usually be cont rolled with a combination of drugs and environmental changes following the
identification of triggers. Attention in developed countries has foc used on asthma because of its rapidly
increasing prevalence, affecting up to one in four urban children. However, asthma is caused by compl ex
interactions of environment al and genetic factors that are not yet fully understood. By the end of 2005 25
genes had been associated with asthma in several populations. Many of these genes are related to the
immune system or to modulating inflammation.

Autoimmune case study

Rheumat oid art hritis (RA) is a chronic and systemic autoimmune dis order, the causes of which are still
incomplet ely known. It most commonly results in the inflammation and tissue damage of joints and tendon
sheaths. RA can be a disabling and painful condition which can ultimately lead to the substantial loss of
function and mobility. Whilst there is currently no known cure for RA, treatment can alleviate symptoms
and in some cases modify the proc ess. Such treatments range from physic al therapy, painkillers and
anti-inflammatory drugs through to disease-modifying antirheumatic drugs (DMA RDs) which can be used
to inhibit the causative immune processes. The course of RA varies greatly with some people having mild
short-term symptoms but, in most cases the disease is progressive and chronic.

Description: When the human immune system fails