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anti-endothelial cell autoantibody 51 antigen-binding cell (ABC) assays
disease. A rim or peripheral pattern of nuclear staining of
cells interacting with antinuclear antibody represents morphologic
expression of anti-double-stranded DNA antibody.
anti-endothelial cell autoantibody
An antibody that may cause vasculitis as part of an autoimmune
response.
anti-epithelial membrane antigen (EMA) antibody
A mouse monoclonal antibody directed against a mucin
epitope present on most human epithelial cells. This antibody
reacts with epithelial mucin, a heavily glycosylated molecule
with a molecular weight of about 400 kDa. Epithelial membrane
antigen is widely distributed in epithelial tissues and
tumors arising from them. Normal glandular epithelium and
tissue from non-neoplastic diseases stain in lumen membranes
and cytoplasm. Malignant neoplasms of glandular epithelium
frequently show a change in pattern with the appearance of
adjacent cell membrane staining. EMA is of value in distinguishing
both large cell anaplastic carcinoma from diffuse
histiocytic lymphoma and small cell anaplastic carcinoma
from well and poorly differentiated lymphocytic lymphomas.
anti-estrogen receptor antibodies
A mouse monoclonal antibody specific for estrogen receptors
(ERs). The ER content of breast cancer tissue is an
important parameter in the prediction of prognosis and
response to endocrine therapy. Monoclonal antibodies to
ER allow determination of the receptor status of breast
tumors in routine histopathology laboratories. Although
monoclonal antibodies that recognize ER were effective
initially only on frozen sections, currently available
monoclonal antibodies are effective on formalin-fixed,
paraffin-embedded tissues for determining ER in routinely
processed and archival material.
anti-Ewing’s sarcoma marker
A mouse monoclonal anti-human MIC2 gene product
(Ewing’s sarcoma marker) antibody reacts only with glioblastoma
and ependymoma of the central nervous system
and certain islet cell tumors of the pancreas. Because the
MIC2 gene products are most strongly expressed on the cell
membranes of Ewing’s sarcoma (ES) and primitive peripheral
neuroectodermal tumors (pPNET), demonstration of the
gene products allows for the differentiation of these tumors
from other round cell tumors of childhood and adolescence.
anti-factor VIII antibody
A mouse monoclonal antibody that gives positive staining in
the cytoplasm of normal vascular endothelial cells of arteries,
veins, capillaries, and endocardial cells. Factor-VIII-related
antigen is also present in megakaryocytes and platelets.
Antifibrillarin antibodies.
antifibrillarin antibodies
Antibodies to this 34-kDa protein constituent of U3 ribonucleoproteins
(RNPs) are detectable in the sera of about
8% of patients with diffuse and limited scleroderma. Also
called anti-U3-RNP antibodies.
antigen
A substance that reacts with the products of an immune
response stimulated by a specific immunogen, including
both antibodies and/or T lymphocyte receptors. Currently
considered to be one of many kinds of substances with
which an antibody molecule or T cell receptor may bind.
These include sugars, lipids, intermediary metabolites,
autocoids, hormones, complex carbohydrates, phospholipids,
nucleic acids, and proteins. By contrast, the “traditional”
definition of antigen is a substance that may
stimulate B and/or T cell limbs of the immune response and
react with the products of that response, including immunoglobulin
antibodies and/or specific receptors on T cells.
See immunogen definition. The “traditional” definition of
antigen more correctly refers to an immunogen. A complete
antigen is one that induces an immune response and
also reacts with the products of the response, whereas an
incomplete antigen or hapten is unable to induce an immune
response alone but is able to react with the products (e.g.,
antibodies). Haptens may be rendered immunogenic by
covalently linking them to a carrier molecule. Following
the administration of an antigen (immunogen) to a host
animal, antibody synthesis and/or cell-mediated immunity
or immunologic tolerance may result. To be immunogenic,
a substance usually needs to be foreign, although some
autoantigens represent exceptions. An immunogen should
usually have a molecular weight of at least 1000 and should
be either a protein or a polysaccharide. Nevertheless, immunogenicity
depends also upon the genetic capacity of the
host to respond to, rather than merely upon, the antigenic
properties of an injected immunogen. The term also alludes
to any molecule capable of producing peptides that unite
specifically with T cell receptors. Refer also to epitope.
antigen–antibody complex
The union of antibody with soluble antigen in solution containing
electrolyte. When the interaction takes place in vitro,
it is called the precipitin reaction, but it may also take place
in vivo. The relative proportion in which antigen and antibody
combine varies according to their molar ratio. Excess antigen
may lead to soluble complexes, whereas excess antibody may
lead to insoluble complexes. In vivo, soluble complexes are
more likely to produce tissue injury, whereas larger insoluble
complexes are often removed by reticuloendothelial system
cells. Also called immune complex.
antigen-binding capacity
Assay of the total capacity of antibody of all immunoglobulin
classes to bind antigen. This refers to primary
as opposed to secondary or tertiary manifestations of
the antigen–antibody interaction. Equilibrium dialysis
measures the antigen-binding capacity of antibodies
with the homologous hapten, and the Farr test measures
primary binding of protein antigens with the homologous
antibody.
antigen-binding cell (ABC) assays
The principle of this assay is the binding of cells bearing
receptors for antigen to a gelatin dish in which antigen is
incorporated. After incubation for a specified time and
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