LESSON 1
IMMUNOHEMATOLOGY
Section I. THE IMMUNE RESPONSE AND THE INTERACTION OF ANTIGENS,
ANTIBODIES, AND COMPLEMENT IN IMMUNOHEMATOLOGY
1-1.
BACKGROUND
Immunology, a field once dominated by bacteriologists, has become important to
scientists in many other areas. The field of immunohematology came into being when
Landsteiner discovered that the blood antigens (ABO) present on RBCs (RBCs) would
react with their respective antibodies present in plasma, and that this reaction had great
clinical significance. Since that time, many discoveries in this field have added to the
understanding of immune mechanisms operative in health and disease. It is important
that scientists working in areas associated with blood transfusion understand basic
immunology and try to be familiar with the recent advances in this field that might relate
directly to their work.
1-2.
THE IMMUME RESPONSE
According to Roitt, the basic of immunology is memory, specificity, and the
recognition of "nonself". The original basis for this was the protection (immunity)
afforded by exposure to infectious illness. The first contact with an infectious organism
imprints some information (for example, memory) so that the body will recognize and
attack that organism when it encounters it in the future. The protection is usually
specific (for example, only against the original infecting organism). The body also has
to recognize that organism as being foreign (that is., "nonself"). The substance initially
responsible for an immune response is known as an antigen or more specifically an
immunogen.
1-3.
ANTIGENS
a. Antigens are substances that can induce a specific immunologic response or
can interact with specific antibody or immune cells "in vivo" or "in vitro". The immune
response can be either humoral or cellular (paragraph 1-4). Blood group serology is
mainly concerned with the humoral response that leads to the production of free
antibody in the plasma. The antibodies, under appropriate conditions of reaction
(temperature, pH, ionic strength, and so forth.), will react specifically with the antigen in
some observable way (for example., agglutination, hemolysis).
b. An antigen contains structural chemical groups in a specific three-dimensional
arrangement, known as antigenic determinants (epitopes), which are lacking or foreign
to the immunized animal. Each antigen can contain many of these epitopes. The
specific three-dimensional shape of these antigenic determinants, or chemical
groupings, is what determines the specificity of its reaction with a particular antibody
molecule.
MD0846
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