CLINICAL LAB SCIENEC

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ESSENTIALS OF CLINICAL LABORATORY SCIENCE
The terms immunology and serology are often used interchangeably. Immunology
more accurately describes the functions of the immune system, while serology
refers to the actual testing of the samples, usually of blood serum. Immunologic
laboratory procedures are based primarily on the reactions of specific antibodies to
antigens, which may be foreign invaders of the body. Antigens may be transplanted
tissue cells, bacteria, viruses, parasites, and even fomites or inanimate (nonliving)
objects such as pollen, chemicals, or toxins that may produce a reaction from the
individual who has been invaded by one of these materials. Immunology differs
from immunohematology (blood banking; see Chapter 17), which is chiefly related
to the deliberate transplantation (transfusion) of blood cells and platelets into a
recipient, to ensuring that blood is free from organisms such as HIV and hepatitis,
and to studying antigens and antibodies associated with blood transfusion and
those complications of pregnancy where a mother may produce antibodies against
the blood of her fetus. Transplanted blood cells may cause a rapid and serious reaction
if they are not compatible with the person receiving the transfusion.
Immunology is based on a study of the components of the immune system
and involves a unified attack by the body against dangerous materials that enter
or attempt to enter the body. The body engineers specific antibodies against
antigens, or foreign invaders, of the body. Once the body has been invaded by
a particular antigen, memory cells (a type of white cell called leukocytes) will
remember the previous invasion, sometimes for the lifetime of the individual.
Each subsequent invasion will precipitate a repeat reaction with a rapid buildup
of antibodies. This rise in the antibody level will provide the basis for immunological
tests. These tests are called serological tests because they use serum to
perform the laboratory procedures. Sometimes the stage to which a disease has
progressed may be determined by the level of antibodies that have been produced
against a specific antigen.
Many quick tests that are easy to perform have become available in the past few
decades. Many of them are quite simple and have been deemed a “waived” test, not
requiring any special training, education, or skills to perform. Tests may be assigned
to the waived category under the Clinical Laboratory Improvement Amendments
of 1988 (CLIA 88), which provide federal government oversight for laboratory
practice. Many of these tests are based on an antibody-antigen reaction.
In some cases, the results for a serological test are reported merely as a positive
or negative response, which is called a qualitative procedure. Semiquantitative
procedures are performed when it is important to determine if the results exceed
the normal levels of antibodies that can be expected when no active disease is
present. Most serological testing is intended to identify the body’s response to
attacking foreign invaders. In autoimmune diseases, the body produces antibodies
against its own tissues or cells. Although no foreign tissue has been transplanted,
the tissues may have become altered and are not recognized as normal
by the immune system. Testing is performed in the same manner for autoimmune
diseases as for responses to bacteria and viruses. A significant number of autoimmune
diseases are covered thoroughly in specific courses related to immunology
and serology. Examples of autoimmune diseases are rheumatoid arthritis (RA)
where joint tissue becomes inflamed and therefore altered, and systemic lupus
erythematosus (SLE), in which antibodies are formed against the nuclear material
of the body’s cells.
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