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triple vaccine 718 tuberculin
halo produced by vasodilation. The third response is a
wheal characterized by swelling and blanching induced
by histamine from mast cell degranulation. The swelling
is attributable to edema between the junctions of cells that
become rich in protein and fluid.
triple vaccine
An immunizing preparation composed of three components
and used to protect infants against diphtheria,
pertussis (whooping cough), and tetanus. It consists of
diphtheria toxoid, pertussis vaccine, and tetanus toxoid.
The first of four doses is administered between 3 and
6 months of age. The second dose is administered 1
month later, and the third dose is given 6 months after
the second. A booster injection is given when a child
begins school.
Triton X-100
A surface-active quaternary ammonium salt (isooctyl
phenoxy polyethoxy ethanol) used as a detergent, emulsifier,
wetting agent, and surfactant.
trophoblast
A layer of cells in the placenta that synthesizes immunosuppressive
agents. The cells are in contact with the uterine lining.
tropical eosinophilia
A hypersensitivity to filarial worms manifested in the lungs
and reported in the Near and Far East. Patients develop
wheezing, productive cough, and a cellular infiltrate
consisting of eosinophils, lymphocytes, and fibroblasts.
Fibrosis may result.
Trypan blue
A vital dye used to stain lymphoid cells, especially in the
microlymphocytotoxicity test used for human leukocyte
antigen (HLA) tissue typing. Cell membranes whose
integrity has been interrupted by antibody and complement
permit the dye to enter and stain the cells dark blue. By
contrast, viable cells with intact membranes exclude the dye
and remain as bright circles of light under a microscope.
Dead cells stain blue.
Trypan blue dye exclusion test
A test for viability of cells in culture. Living cells exclude
Trypan blue by active transport. When membranes have
been interrupted, dye enters the cells, staining them blue,
indicating the cells are dead. The method can be used to
calculate the percent of cell lysis induced.
trypanosome adhesion test
Selected mammalian red blood cells or bacteria may stick
to the surfaces of trypanosomes when specific antibody and
complement are present. This characteristic was used in the
past as a test for antibodies to trypanosomes.
trypanosome immunity
Vaccination against African sleeping sickness known as
trypanosomiasis has thus far been unattainable. Although
the antigen that induces a protective humoral response
is well known as a surface glycoprotein that covers the
entire trypanosome, the organism repeatedly changes the
antigenic structure of this glycoprotein (variant surface
glycoprotein, VSG), thereby evading destruction by the
host immune response. Only a single VSG is expressed by
a trypanosome at one time. Trypanosomes that express the
same VSG are classified as belonging to the same variable
antigenic type (VAT). Only short-term immunity can be
induced by allowing cattle to become infected by fly bites
and then treating the infection as soon as the parasitemia
becomes patent. The powerful humoral response in trypanosomal
infections is characterized by the appearance of
immunoglobulin M (IgM) and IgG antibodies associated
with the elimination of each VAT. These antibodies kill
parasites and clear them from the blood by complement
activation by way of the classic pathway and opsonization,
which results in uptake by the Kupffer’s cells of the
liver. The immune response in experimental mice consists
of both T-dependent and T-independent components.
Lymphocyte responsiveness is profoundly depressed in
trypanosome infections.
tryptic peptides
Peptides formed by tryptic digestion of protein.
Ts
(1) Suppressor T lymphocyte. (2) Secreted immunoglobulin
heavy chain tail (C terminal) polypeptide.
Ts1, Ts3 lymphocytes
Suppressor T lymphocyte subpopulations.
TsF
Abbreviation for suppressor T cell factor.
Ts cells
CD8 + /D57 + /CD28 - regulatory T cells considered to downregulate
immune responses. Interaction of a Ts cell with an
antigen presenting cell pMHC leads to tolerization of the
antigen presenting cell through suppression of B7 expression
and upregulation of ILT3 and ILT4. CD4 + Th0 cells are
rendered anergic and/or develop into T reg cells after interaction
with the antigen presenting cells. When Ts cells become
activated, they synthesize a Th0-like profile of cytokines.
TSA
Abbreviation for tumor-specific antigen.
TSF
T cell suppressor factor.
TTF-1 (8G7G3/a), mouse
Thyroid transcription factor-1 is useful in differentiating
primary adenocarcinoma of the lung from metastatic carcinomas
from the breast and malignant mesothelioma. It can
also be used to differentiate small cell lung carcinoma from
lymphoid infiltrates.
tube agglutination test
An agglutination assay that consists of serial dilutions of
antiserum in serological tubes to which a particulate antigen
such as a microorganism is added.
tuberculid
A hypersensitivity skin reaction to mycobacteria. The lesion
may be a papulonecrotic tuberculid with sterile papules
ulcerated in the center and obliterative vasculitis, or crops
of small red papules with sarcoid-like appearances that
represent lichen scrofulosorum.
tuberculin
A sterile solution containing a group of proteins derived
from culture medium in which Mycobacterium tuberculosis
microorganisms have been grown. It has been used
for almost a century as a skin test preparation to detect
delayed-type (type IV) hypersensitivity to infection with M.
tuberculosis. Many tuberculin preparations have been used
in the past, but only old tuberculin (OT) and purified protein
derivative (PPD) are still used. While OT is a heat-concentrated
filtrate of the culture medium in which M. tuberculosis
was grown, PPD of tuberculin is a trichloroacetic acid
precipitate of the growth medium. Tuberculin is a mitogen
for murine B lymphocytes and also a T lymphocyte mitogen.