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immunologist 381 immunophenotyping
Sertoli cells of the testes express Fas ligand. Immune
privilege is a consequence not only of the lack of an
inflammatory response but also the immune consequences
of the accumulation of apoptotic immune cells
within a tissue. Immune cell apoptosis may be a signal
to terminate inflammation. Apoptotic cell accumulation
during an immune response may activate the development
of cells that function to downregulate or suppress further
immune activation. Thus, immunosuppression by physical
barriers, hormone secretion, low numbers of dendritic
cells, immune deviation, immunosuppressive cytokines,
or Fas killing may facilitate the induction of immunological
privilege.
immunologist
A person who makes a special study of immunology.
immunology
The branch of biomedical science concerned with the
responses of organisms to immunogenic (antigenic) challenges,
the recognition of self from nonself, and all the
biological (in vivo), serological (in vitro), physical, and
chemical aspects of immune phenomena.
immunolymphoscintigraphy
A method to determine the presence of tumor metastasis in
lymph nodes. Antibody fragments or monoclonal antibodies
against specific tumor antigens are radiolabeled and then
detected by scintigraphy.
immunomagnetic technique
The use of magnetic microspheres to sort, isolate, or identify
cells with specific antigenic determinants.
immunomodulation
Therapeutic alteration of the immune system by the administration
of biological response modifiers such as lymphokines
or antibodies against cell surface markers bound to a
toxin such as ricin.
immunomodulator
An agent that alters the level of an immune response.
immunopathic damage
Collateral injury to host tissues induced by cytokines and
effector cells released in the course of an immune response.
immunonephelometry
A test that measures light scattered at a 90° angle to a
laser or light source as it is passes through a suspension of
minute complexes of antigen and antibody. Measurement is
made at 340 to 360 nm using a spectrophotometer.
immunoosmoelectropheresis
Refer to counter immunoelectrophoresis.
immunoparasitology
Immunologic aspects of the interactions between animal
parasites and their hosts.
immunopathic
Injury to cells, tissues, or organs induced by either humoral
(antibodies) or cellular products of an immune response.
immunopathology
The study of disease processes that have immunological
etiology or pathogenesis involving either humoral antibody
(from B cells) and complement or T-cell-mediated or
cytokine mechanisms. Immunologic injury of tissues and
cells may be mediated by any of the four types of hypersensitivity
(described separately).
immunoperoxidase method
Nakene and Pierce in 1966 first proposed that enzymes be
used in the place of fluorochromes as labels for antibodies.
Horseradish peroxidase (HRP) is the enzyme label most
widely employed. The immunoperoxidase technique
permits the demonstration of antigens in various types of
cells and fixed tissues. This method has certain advantages:
(1) conventional light microscopy is used, (2) stained
preparations may be kept permanently, (3) the method may
be adapted for use with electron microscopy of tissues,
and (4) counterstains may be employed. The disadvantages
include: (1) the demonstration of relatively minute,
positively staining areas is limited by the resolution of
the light microscope, (2) endogenous peroxidase may not
have been completely eliminated from the tissue under
investigation, and (3) diffusion of products results from
enzyme reactions away from the area where antigen is
localized. The peroxidase–antiperoxidase (PAP) technique
employs unlabeled antibodies and a PAP reagent. It
has proven highly successful for demonstrating antigens
in paraffin-embedded tissues as an aid in surgical pathologic
diagnosis. Tissue sections preserved in paraffin are
first treated with xylene; after deparaffinization they are
exposed to a hydrogen peroxide solution that destroys the
endogenous peroxidase activity in tissue. The sections are
next incubated with normal swine serum, which suppresses
nonspecific binding of immunoglobulin molecules to tissues
containing collagen. Thereafter, the primary rabbit
antibody against the antigen to be identified is reacted with
the tissue section. Unbound primary antibody is removed
by rinsing the sections that are then covered with swine
antibody against rabbit immunoglobulin. This so-called
linking antibody will combine with any primary rabbit
antibody in the tissue. It is added in excess, which causes
one of its antigen-binding sites to remain free. After
washing, the PAP reagent is placed on the section, and
the antibody portion of this complex, which is raised in
rabbits, will be bound to the free antigen-binding site of
the linking antibody on the sections. The unbound PAP
complex is then washed away by rinsing. To read the sections
microscopically, it is necessary to add a substrate of
hydrogen peroxide and aminoethylcarbazole (AEC), which
permits the formation of a visible product that may be
detected with a light microscope. The AEC is oxidized to
produce a reddish-brown pigment that is not water soluble.
Peroxidase catalyzes the reaction. Because peroxidase
occurs only at sites where the PAP is bound via linking
antibody and primary antibody to antigen molecules, the
antigen is identified by the reddish-brown pigment. The tissue
sections can then be counterstained with hematoxylin
or other suitable dye, covered with mounting medium and
cover slips, and read by conventional light microscopy. The
PAP technique has been replaced, in part, by the avidin–
biotin complex (ABC) technique.
immunophenotyping
The use of monoclonal antibodies and flow cytometry to
reveal cell surface or cytoplasmic antigens that yield information
that may reflect clonality and cell lineage classification.
This type of data is valuable clinically in aiding the
diagnosis of leukemias and lymphomas through the use of
a battery of B cell, T cell, and myeloid markers. However,
immunophenotyping results must be used only in conjunction
with morphologic criteria when reaching a diagnosis of
leukemia or lymphoma.
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