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sequential determinant 646 serology
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G F E D C B A
Example of high resolution DRB1 typing using sequence-specific primer
methodology. Molecular weight ladder of known base pairs for base pair
sizing appears at far left.
and the PCR reaction is initiated under stringent conditions,
a perfectly matched primer pair results in an amplification
product. A mismatch at the 3′ end primer pair will not
provide any amplification product. A positive result (amplification)
defines the specificity of the DNA sample. The PCR
amplification step provides the basis for identifying polymorphism.
The post-amplification processing of the sample
consists only of a simple agarose gel electrophoresis to detect
the presence or absence of amplified product. DNA-amplified
fragments are visualized by ethidium bromide staining and
exposure to ultraviolet light. A separate technique detects
amplified product by color fluorescence. The primer pairs
are selected in such a manner that each allele should have
a unique reactivity pattern with the panel of primer pairs
employed. Appropriate controls must be maintained.
sequential determinant
An epitope whose specificity is determined by the sequence
of several residues within the antigenic determinant rather
than by the molecular configuration of the antigen molecule.
A peptide segment of approximately six amino acid
residues represents the sequential determinant structure.
sequestered antigen
An antigen that is anatomically isolated and not in contact
with the immunocompetent T and B lymphoid cells of the
immune system. Examples include myelin basic protein, sperm
antigens, and lens protein antigens. When a sequestered antigen
is released by one or several mechanisms including viral
inflammation, it can activate immunocompetent T and B cells.
An example of the sequestered antigen release mechanism of
autoimmunity is found in experimental and post-infectious
encephalomyelitis. Cell-mediated injury represents the
principal mechanism in this disease. In vasectomized males,
Host cell
Antigen
processed,
Presented
to T cell
T
Normally sequestered antigen
Cell-mediated
autoimmunity
Signal
Autoantibody to sequestered antigen
Release of sequestered antigen.
antisperm antibodies are known to develop when sperm antigens
become exposed to immunocompetent lymphoid cells.
Likewise, lens protein of the eye that enters the circulation
as a consequence of crushing injury to the eye or exposure of
lens protein to immunocompetent cells inadvertently through
surgical manipulation may lead to an antilens protein immune
response. Autoimmunity induced by sequestered antigens is
relatively infrequent and a rare cause of autoimmune disease.
serial dilution
The successive dilution of antiserum in a row of serological
tubes containing physiologic saline solution as diluent to
yield the greatest concentration of antibody in the first tube
and the lowest in the last tube that contains the highest dilution.
For example, a double quantity of antiserum is placed
in the first tube, half of which is transferred to the second
tube containing an equal volume of diluent. After thorough
mixing with a serological pipette, an equivalent amount is
transferred to the next tube. The process continues and the
volume removed from the last tube in the row is discarded.
This represents a doubling dilution.
serial passage
A method to attenuate a pathogenic microorganism but
retain its immunogenicity by transfer through several animal
hosts, growth media, or tissue culture cells.
serial TC triggering model
A design dependent on the hypothesis that relatively few
pMHC complexes can interact successively with enough T
cell receptors to yield the sustained signaling requisite for
naïve T cell total activation.
seroconversion
The first appearance of specific antibodies against a causative
agent in the blood during the course of an infection or
following immunization.
serological determinants
Epitopes on cells that react with specific antibody and
complement, leading to fatal injuries of cells. Serological
determinants are to be distinguished from lymphocyte
determinants that are epitopes on cell surfaces to which sensitized
lymphocytes are directed, leading to cell destruction.
Although the end result is the same, antibodies and lymphocytes
are directed to different epitopes on cell surfaces.
serological epitope
An antigenic determinant reactive with a specific antibody
or group of antibodies.
serologically defined (SD) antigens
Mammalian cellular membrane epitopes encoded by
major histocompatibility complex genes. Antibodies
detect these epitopes.
serology
The study of the in vitro reactions of antibodies in serum
with antigens (usually those of microorganisms inducing
infectious disease).
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