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streptolysin O test 669 Strongyloides hyperinfection
against phosphocholine-containing epitopes of the pneumococcal
cell wall. This antibody does not appear protective
in human subjects; reaction between the antibody and the
bacterial cell wall occurs beneath the capsule. The complement
fragments and bound Fc are inaccessible to phagocytic
cells. Vaccines to prevent streptococcal infections are
hindered by the systemic local and systemic reactions that
follow administration of large does of M protein given in an
effort to induce type-specific antibody responses. This may
be attributable to M proteins serving as superantigens. Heartreactive
epitopes have been removed from M proteins, which
has made possible immunization with purified M protein
preparations to induce type-specific opsonic antibodies that
do not cross react with heart antibodies. Immunization protocols
also included attempts to stimulate antibodies against
lipoteichoic acid, the adherence constituent of streptococci,
but these efforts have been limited by the poor immunogenicity
of this component. Vaccination with capsular polysaccharides
is effective in preventing pneumococcal infection.
streptolysin O test
Refer to ASO.
stress and immunity
Stressors can alter many facets of the immune response.
Numerous bidirectional pathways of communication connect
the immune system and the brain, and stress may
function through this neuroimmune network to influence
immune responses. However, the different types of stress
and different means of stress perception lead to the production
of different combinations of autonomic activations
and hormones. Immune system-derived information may
act on the nervous system, such as during an infection, and
may also trigger changes in behavior patterns that resemble
stress-associated behavior. The immune system may serve
as a sensory organ, transmitting to the brain information
about antigens through lymphocyte-derived hormones
while being modulated by neural factors (stress-related or
otherwise). Immune, neural, and psychosocial realms may
be coordinated as coherent processes allow identification
of the context, interpretation, and meaning of stress for an
individual to determine the effects on immunity.
stress proteins
Stress proteins are characterized into major families, generally
by molecular weights. Heat shock proteins show a high
degree of sequence homology throughout the phylogenetic
spectrum and are among the most highly conserved proteins
in nature. Heat shock protein 70 from mycobacteria and
humans reveals 50% sequence homology. In spite of this
homology, subtle differences exist in the functions, inducibility,
and cellular locations of related heat shock proteins for
a given species. Although major stress proteins accumulate
to very high levels in stressed cells, they are present at low
to moderate levels in unstressed cells, indicating that they
play a role in normal cells. In addition to increased synthesis,
many heat shock proteins change their intracellular distribution
in response to stress. An important characteristic is
their capacity to function as molecular chaperones, reflecting
their capacity to bind to denatured proteins, preventing their
aggregation; this helps explain the functions of heat shock
proteins under normal conditions and in stress situations.
striational antibodies
Antibodies demonstrable in 80 to 100% of myasthenia gravis
(MG) patients with thymoma; they are not present in 82 to
100% of patients with MG who do not have thymoma. If striational
antibodies are not demonstrable in a patient with MG,
the individual probably does not have thymoma. One quarter
of patients with rheumatoid arthritis receiving penicillamine
therapy develop immunoglobulin M (IgM) striational antibodies.
Patients receiving immunosuppressive therapy may also be
monitored for striational antibodies to detect the development of
autoimmune reactions following bone marrow transplantation.
T cell receptor
(TCR)
MHC class II
molecule
T cell
Antigen presenting cell
Superantigen.
Superantigen
striational autoantibodies (StrAbs)
Autoantibodies associated with thymoma in patients with
myasthenia gravis (MG). Thymoma occurs in 10% of MG
patients and MG occurs in 15 to 80% of patients with
thymoma. Striational antibodies react with proteins in the
contractile constituents of skeletal muscle. The relevant
epitopes remain to be demonstrated. Autoantigens reactive
with striational autoantibodies include actin, α-actinin,
myosin, and titin (connectin). The ryanodine receptor
(sarcoplasmic reticulum calcium release channel protein).
Striational autoantibodies can be detected by immunofluorescence
using cryostat sections of skeletal muscle—the
method of choice for striational autoantibody screening.
These autoantibodies are most often found in MG patients
over 60 years of age. The autoantibodies are present in 80 to
90% of patients with both MG and thymoma, in approximately
30% of patients with acquired (adult onset) MG,
and in 24% of patients with thymoma without clinical signs
of MG. Striational autoantibodies are absent in more than
70% of patients with MG without thymoma; thus, they are
very sensitive and specific for thymoma in MG patients, and
their absence rules out a diagnosis of thymoma in MG.
stromal cells
Sessile cells that form an interconnected network that gives
an organ structural integrity but also provides a specific
inductive microenvironment that facilitates differentiation
and maturation of incoming precursor cells. Stromal cells
and their organization are fully as complex as the cells
whose development they regulate. For example, stromal
cells of the thymus are the best characterized with respect
to their role in T lymphocyte maturation.
Strongyloides hyperinfection
Strongyloides stercoralis larvae may invade the tissues
of immunosuppressed patients with enteric strongyloides
infection to produce this condition.
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