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estitope 619 reticulin autoantibodies
Resting lymphocyte
12 µm
Resting lymphocyte.
Activated lymphocyte
nucleus usually has a poorly visible single indentation and
contains densely packed chromatin. Occasionally, nucleoli
can be distinguished. The small lymphocyte variant—the
predominant morphologic form—is slightly larger than an
erythrocyte. Larger lymphocytes ranging from 10 to 20 μm
in diameter are difficult to differentiate from monocytes.
They have more cytoplasm and may show azurophilic
granules. Intermediate-size forms are also described. Under
phase contrast microscopy, living lymphocytes show feeble
motility with amoeboid movements that give the cells
hand-mirror shapes. The mirror handle is called a uropod.
In large lymphocytes, mitochondria and lysosomes are
better visualized, and some cells show spherical, birefringent,
0.5-μm diameter inclusions called Gall bodies.
Lymphocytes do not spread on surfaces. The different
classes of lymphocytes cannot be distinguished by light
microscopy. B lymphocytes sometimes show hairy (rough)
surfaces under scanning electron microscopy (SEM), but
thes are apparently artifacts. Electron microscopy does not
provide additional information except for visualization of
cellular organelles that are not abundant. This suggests that
the small resting lymphocytes are end-stage cells; however,
under appropriate stimulation, they are capable of considerable
morphologic changes.
restitope
That segment of a T cell receptor that makes contact and
interacts with a class II histocompatibility antigen molecule
during antigen presentation.
restriction endonucleases
Bacterial products that identify and combine with a short
sequence of DNA. The enzyme acts as molecular scissors
by cleaving the DNA at the recognition site or at another
location. Restriction endonucleases catalyze degradation
of foreign DNA. They recognize precise base sequences
of DNA and cut it into relatively few fragments, termed
restriction fragments. The three major types of restriction
endonucleases are (1) type I enzymes that identify specific
base sequences but cut the DNA elsewhere (approximately
1000 bp from the recognition site); (2) type II enzymes that
identify specific base sequences and cut the DNA within or
adjacent to these sequences; and (3) type III endonucleases
that identify specific base sequences and cut the DNA
approximately 25 bp from the recognition site.
restriction fragment-length polymorphism (RFLP)
Genome diversity in DNA from different subjects revealed
by restriction map comparisons. This diversity is based
on differences in restriction fragment lengths determined
by sites of restriction endonuclease cleavage of the DNA
molecules and revealed by preparing southern blots using
appropriate molecular hybridization probes. Polymorphisms
may be demonstrated in exons, introns, flanking sequences,
or any DNA sequence. Variations in DNA sequence show
Mendelian inheritance. Results are useful in linkage studies
and can help to identify defective genes associated with
inherited disease.
restriction map
A diagram of a linear or circular molecule of DNA
that indicates the points where one or more restriction
enzymes cleave the DNA. DNA is first digested with
restriction endonucleases that split the DNA into fragments
that can be separated by gel electrophoresis. Size
determination is accomplished by comparison with fragments
of known size.
reticular cell
Stroma or framework cells that, with reticular fibers, constitute
the lymphoid tissue framework of lymph nodes, spleen,
and bone marrow.
reticular dysgenesis
The most severe form of all combined immunodeficiency
disorders. Leads to a failure in the development of B cells, T
cells, NK cells, and granulocytes. This condition is incompatible
with life and leads to early death of affected infants.
The only possibility for treatment is hematopoietic stem cell
transplantation or bone marrow transplantation. This condition
has an autosomal-recessive mode of inheritance.
reticulin antibodies
Antibodies of five separate types of which the R 1 RA is of
greatest interest. Immunoglobulin A (IgA) R 1 ARAs show
more than 98% specificity for untreated celiac disease;
however, sensitivity is only 20 to 25%.
Reticulin autoantibodies.
reticulin autoantibodies
R 1 ARA is the only one of five separate reticulin autoantibodies
that has diagnostic and pathogenic significance. IgA
R 1 ARAs are highly specific for untreated celiac disease
(CD). Approximately 2.6% of healthy children possess
reticulin autoantibodies. In IgA-deficient subjects under
evaluation for CD, the detection of IgG ARA, IgG gliadin
autoantibodies (AGA), and IgG endomysial autoantibodies
(EmAs) may be helpful. R 1 ARAs classically disappear 3 to
12 months following the maintenance of a strict gluten-free
diet in both adults and children with CD. IgA, ARA, IgA
AGA, and IgA EmA may be detected in dermatitis herpetiformis
(DH).
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