Untitled - D Ank Unlimited

Sézary syndrome 650 Shwartzman (or Shwartzman–Sanarelli) reaction
Sézary syndrome
A disease that occurs in middle age, affecting males more
commonly than females. It is a neoplasm (malignant lymphoma
of CD4 + T helper lymphocytes with prominent skin
involvement). Generalized erythroderma, hyperpigmentation,
and exfoliation are observed. Fissuring and scaling
of the skin on the palms of the hands and soles of the feet
may occur. The peripheral blood and lymph nodes contain
the typical cerebriform cells that have nuclei that resemble
the brain. Infiltration of the skin by leukocytes is extensive,
with prominent clustering in the epidermis forming
Pautrier’s abscesses. Late in the disease, T immunoblasts
may appear. The so-called Sézary cells are T lymphocytes.
This syndrome is an advanced type of mycosis fungoides.
SH2 domain
Refer to Src family tyrosine kinases.
shared haplotype
Phenotypic characteristic shared by two siblings based on
closely linked genes on one chromosome inherited from each
parent. There are four different possibilities of reassortment
among offspring, which leads to a particular sibling pair
sharing two, one or no haplotypes. Selected haplotypes are
in strong linkage disequilibrium between alleles of different
loci. According to Mendelian genetics, 25% of siblings will
share both haplotypes. Siblings are much more likely to share
one or two haplotypes than are unrelated individuals.
sheep red blood cell agglutination test
An assay in which sheep erythrocytes are agglutinated
by antibody or are used as carrier particles for an antigen
adsorbed to their surfaces, in which case they are passively
agglutinated by antibodies specific for the adsorbed antigen.
shift assay
A useful method for identifying protein–DNA interactions
that may mediate gene expression, DNA repair, or
DNA packaging. The assay can also be used to determine
the affinity abundance, binding constants, and binding
specificity of DNA-binding proteins. The gel shift assay is
performed by annealing two labeled oligonucleotides that
contain the test binding sequence, then incubating the duplex
with the binding protein. The mixture is then separated on
a nondenaturing polyacrylamide gel. Duplexes bound by
protein migrate more slowly than unbound duplexes and
appear as bands that are shifted relative to the bands from
the unbound duplexes. Also called gel mobility shift assay,
gel shift assay, gel retardation, or band shift assay.
Shigella immunity
The host protective immune response to Shigella infection
is poorly understood. Because M cells of the gut take up
the microorganisms, secretory immunoglobulin A (IgA)
immune responsiveness has been postulated to be protective
in shigellosis, but this has been difficult to establish.
The immunity induced is type-specific, with reinfection
occurring only within different Shigella species or
serotypes. This immunity is believed to be associated with
an immune response to lipopolysaccharide determinants.
Shigella may destroy antigen-presenting cells in a host following
systemic exposure to Shigella antigens and toxins
before an immune response can be established. Serum
IgG has no protective effect. Oral vaccines with attenuated
Shigella induce type-specific protection. Previous
Shigella infection leads to specific IgA secretion in breast
milk. Antibodies develop early against somatic Shigella
antigens. Shiga toxin is a multimeric protein comprised of
a single enzymatically active A subunit and five B subunits
needed for toxin binding. It is synthesized only by Shigella
dysenteriae type I strains and is an important virulence
factor in the pathogenesis of hemolytic–uremic syndrome
that may be a complication of infection. Shiga toxin induces
IgM antibody responses, but the IgG response is lacking;
however, IgG can be raised against Shiga toxin in animal
models. Protection against Shigella has been associated
with the humoral response to lipopolysaccharide (LPS) or
plasmid-encoded protein antigens. T cells also become activated
in vivo during Shigella infection. There may be some
correlation between T cell activation and disease severity.
Local cytokine synthesis is also significant in shigellosis.
Increased levels of interleukin-1 (IL1), IL6, tumor necrosis
factor (TNF), and interferon-γ (IFN-γ) have been found
in stool specimens and plasma of infected patients. Both
Th1 and Th2 cytokines are present in shigellosis. Humoral
and cytotoxic defense mechanisms may be present during
infection. High serum antitoxin titers failed to protect
monkeys against intestinal disease following challenge with
live Shigella dysentariae. Heat-killed whole cell Shigella
vaccines failed to protect. Post-infection reactive arthritis
may occur. Although mucosal secretory IgA is thought to
prevent bacterial attachment to the mucosa and neutralize
toxins, the significance of these mechanisms in shigellosis
has not been proven.
shingles (herpes zoster)
A virus infection that occurs in a band-like pattern according
to distribution in the skin of involved nerves. It is usually
a reactivation of the virus that causes chickenpox.
SHIV
Simian–human immunodeficiency virus. A SIV mac and
HIV-1 chimera capable of infecting macaques, it possesses
the HIV genes ENV, Tat, Rev, and Vpu, with its remaining
genes derived from SIV mac.
shocking dose
The amount of antigen required to elicit a particular clinical
response or syndrome.
shock organ
An organ involved in a specific reaction such as an anaphylactic
reaction.
short-lived lymphocytes
Lymphocytes with lifespans of 4 to 5 days, in contrast to
long-lived lymphocytes that may exist in blood circulation
from months to years.
Shulman, Sidney
Professor of microbiology and immunology at the
University of Buffalo who performed important work on
immune aspects of human infertility.
Shwartzman, Gregory (1896–1965)
Russian–American microbiologist who described systemic
and local reactions that follow injection of bacterial endotoxins.
The systemic Shwartzman reaction, a nonimmunologic
phenomenon, is related to disseminated intravascular
coagulation. The local Shwartzman reaction in skin resembles
the immunologically based Arthus reaction in appearance.
(Refer to Phenomenon of Local Tissue Reactivity and
Its Immunological and Clinical Significance, 1937.)
Shwartzman (or Shwartzman–Sanarelli) reaction
A nonimmunologic phenomenon in which endotoxin
(lipopolysaccharide) induces local and systemic reactions.