Microbiology and Immunology

Autologous banking WORLD OF MICROBIOLOGY AND IMMUNOLOGY

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See alsoBacterial movement; Heat shock response

AUTOCLAVE•seeSTEAM PRESSURE STERILIZER

AUTOIMMUNITY AND AUTOIMMUNE

DISORDERSAutoimmunity and autoimmune disorders

Autoimmune diseases are conditions in which a person’s

immune systemattacks the body’s own cells, causing tissue

destruction. Autoimmune diseases are classified as either gen-

eral, in which the autoimmune reaction takes place simultane-

ously in a number of tissues, or organ specific, in which the

autoimmune reaction targets a single organ. Autoimmunity is

accepted as the cause of a wide range of disorders, and is sus-

pected to be responsible for many more. Among the most

common diseases attributed to autoimmune disorders are

rheumatoid arthritis, systemic lupus erythematosis (lupus),

multiple sclerosis, myasthenia gravis, pernicious anemia, and

scleroderma.

To further understand autoimmune disorders, it is help-

ful to understand the workings of the immune system. The

purpose of the immune system is to defend the body against

attack by infectious microbes (germs) and foreign objects.

When the immune system attacks an invader, it is very spe-

cific—a particular immune system cell will only recognize

and target one type of invader. To function properly, the

immune system must not only develop this specialized knowl-

edge of individual invaders, but it must also learn how to rec-

ognize and not destroy cells that belong to the body itself.

Every cell carries protein markers on its surface that identifies

it in one of two ways: what kind of cell it is (e.g., nerve cell,

muscle cell, blood cell, etc.) and to whom that cell belongs.

These markers are called major histocompatibility complexes

(MHCs). When functioning properly, cells of the immune sys-

tem will not attack any other cell with markers identifying it

as belonging to the body. Conversely, if the immune system

cells do not recognize the cell as “self,” they attach themselves

to it and put out a signal that the body has been invaded, which

in turn stimulates the production of substances such as anti-

bodies that engulf and destroy the foreign particles. In case of

autoimmune disorders, the immune system cannot distinguish

between self cells and invader cells. As a result, the same

destructive operation is carried out on the body’s own cells

that would normally be carried out on bacteria, viruses, and

other such harmful entities.

The reason why the immune system become dysfunc-

tional is not well understood. Most researchers agree that a

combination of genetic, environmental, and hormonal factors

play into autoimmunity. The fact that autoimmune diseases

run in families suggests a genetic component. Recent studies

have identified an antiphospholipid antibody(APL) that is

believed to be a common thread among family members with

autoimmune diseases. Among study participants, family mem-

bers with elevated APL levels showed autoimmune disease,

while those with other autoantibodies did not. Family mem-

bers with elevated APL levels also manifested different forms

of autoimmune disease, suggesting that APL may serve as a

common trigger for different autoimmune diseases. Further

study of the genetic patterns among unrelated family groups

with APL suggests that a single genetic defect resulting in

APL production may be responsible for several different

autoimmune diseases. Current research focuses on finding an

established APL inheritance pattern, as well as finding the

autoimmune generesponsible for APL production.

A number of tests can help diagnose autoimmune dis-

eases; however the principle tool used by physicians is anti-

body testing. Such tests involve measuring the level of

antibodies found in the blood and determining if they react

with specific antigens that would give rise to an autoimmune

reaction. An elevated amount of antibodies indicates that a

humoral immune reaction is occurring. Elevated antibody lev-

els are also seen in common infections. These must be ruled

out as the cause for the increased antibody levels. The anti-

bodies can also be typed by class. There are five classes of

antibodies and they can be separated in the laboratory. The

class IgG is usually associated with autoimmune diseases.

Unfortunately, IgG class antibodies are also the main class of

antibody seen in normal immune responses. The most useful

antibody tests involve introducing the patient’s antibodies to

samples of his or her own tissue—if antibodies bind to the tis-

sue it is diagnostic for an autoimmune disorder. Antibodies

from a person without an autoimmune disorder would not

react to self tissue. The tissues used most frequently in this

type of testing are thyroid, stomach, liver, and kidney.

Treatment of autoimmune diseases is specific to the dis-

ease, and usually concentrates on alleviating symptoms rather

than correcting the underlying cause. For example, if a gland

involved in an autoimmune reaction is not producing a hor-

mone such as insulin, administration of that hormone is

required. Administration of a hormone, however, will restore

the function of the gland damaged by the autoimmune disease.

The other aspect of treatment is controlling the inflammatory

and proliferative nature of the immune response. This is gen-

erally accomplished with two types of drugs. Steroid com-

pounds are used to control inflammation. There are many

different steroids, each having side effects. The proliferative

nature of the immune response is controlled with immunosup-

pressive drugs. These drugs work by inhibiting the replication

of cells and, therefore, also suppress non-immune cells lead-

ing to side effects such as anemia. Prognosis depends upon the

pathology of each autoimmune disease.

See alsoAntigens and antibodies; Antibody formation and

kinetics; Antibody-antigen, biochemical and molecular reac-

tions; Immune system; Immunity, cell mediated; Immunity,

humoral regulation; Immunologic therapies; Immunosup-

pressant drugs; Major histocompatibility complex (MHC)

AAutologous bankingUTOLOGOUS BANKING

Autologous banking is the recovery and storage of an individ-

ual’s own blood. The blood can be from the circulating blood,

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