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T1DM
Abbreviation for type 1 diabetes mellitus.
T2DM
Abbreviation for type 2 diabetes mellitus.
T4 count
An abbreviated clinical term designating the number of
CD4 + T cells in the blood. Normal value is 800 to 1100
CD4 + T cells/mm 3 blood.
T-200
An obsolete term for leukocyte common antigen (CD45).
TAA
Abbreviation for tumor-associated antigen.
TAB vaccine
An immunizing preparation used to protect against enteric
fever. It is composed of Salmonella typhi and S. paratyphi
A and B microorganisms killed by heat and preserved with
phenol. The bacteria used in the vaccine are in the smooth
specific phase and contain both O and Vi antigens. The vaccine
is administered subcutaneously. Lipopolysaccharide from the
Gram-negative bacteria may induce fever in vaccine recipients.
If S. paratyphi C is added, the vaccine is known as TABC. If
tetanus toxoid is added, it is referred to as TABT.
Tac
A cell surface protein on T lymphocytes that binds interleukin-2
(IL2). It is a 55-kDa polypeptide (p55) expressed
on activated T lymphocytes. Tac is an abbreviation for T
activation. The p55 Tac polypeptide combines with IL2
with a K d of about 10 –8 M. Interaction of IL2 with p55 alone
does not lead to activation. IL2 binds to a second protein
termed p70 or p75 that has a higher binding affinity to p55.
T cells expressing p70 or p75 alone are stimulated by IL2.
Cells that express both receptor molecules bind IL2 more
securely and can be stimulated with a relatively lower IL2
concentration compared to stimulation when p70 or p75
alone interacts with IL-2. Anti-Tac monoclonal antibody
can inhibit T cell proliferation.
Tac antigen
Refer to CD25.
TACI (transmembrane activator and CAML-interactor)
A tumor necrosis factor (TNF) receptor family member
that serves as one of the two major receptors for BLyS.
Dendritic cells, B cells, and T cells all express the TACI
receptor, which is believed to be important for receiving
signals from BLyS.
tacrolimus
An immunosuppressive polypeptide agent administered to
allotransplant recipients to suppress their T cells through
inhibition of signal transduction from T cell receptors.
Refer to FK506.
T activation
The use of bacterial neuraminidase to cleave N-acetyl
(sialic acid) residue to uncover masked or hidden antigenic
determinants (epitopes). This permits agglutination of the
T
treated cells by natural antibodies in the blood of most
individuals. Aged blood can be used to detect T activation.
Taenia solium immunity
Pre-encystment (early) immunity is defined as the immune
response at the oncosphere penetration site. Late post-oncospheral
or post-encystment immunity is the immune response
at the final establishment site. Secretory immunoglobulin A
(IgA) in gut secretions likely attacks invading oncospheres,
as it is resistant to intestinal enzymes. Mast cells surround
invading oncospheres and developing larvae, suggesting
that IgE may react with antigen, leading to degranulation of
cells whose products cause increased vascular permeability.
This would permit IgG antibodies to reach the invading site.
Eosinophils also surround invading oncospheres, but no evidence
indicates that they induce injury. When newly hatched
oncospheres reach their establishment site, they transform
from a stage in which they are highly vulnerable to attack to
one in which they are completely resistant. Both humoral and
cellular responses to T. solium are heterogeneous in pigs and
humans. Ninety percent of the serum antibody is IgG. The
T. solium cysticerci induce a chronic granulomatous reaction
in pig muscle with extensive eosinophil infiltration and
degranulation. T cell immunity to larval cestodes remains to
be demonstrated. Larval cestodes may contain blocking antibodies
on the surface. Molecular mimicry is also believed
to represent an evasive strategy whereby this parasite avoids
the host immune response. Some larvae produce inhibitors
of proteolytic enzymes such as trypsin and chymotrypsin
and some may induce immunosuppression of the host.
Vaccination with living eggs can induce complete protection
against challenge infection, but egg supplies are limited.
This has been remedied by the development of recombinant
taeniid vaccine antigens that have been able to induce protection
in animals.
TAFs
Abbreviation for toxoid antitoxin floccules.
T agglutinin
An antibody that occurs naturally in the sera of humans. It
agglutinates red blood cells expressing T antigen as a result
of their exposure to bacteria or treatment with neuraminidase.
This antibody is of interest in transfusion medicine as
it may confuse blood grouping or cross matching by giving
a false-positive reaction when red blood cell suspensions
contaminated with microorganisms are used.
tag
A molecular label employed to render unitary antigen–
antibody combinations detectable. Substances frequently
used as tags include radioisotopes, enzymes, fluorochromes,
and electron-dense materials that may be united covalently
to the antigen or antibody portion of a complex.
Tagliacozzi, Gaspare (1545–1599)
Physician of Bologna who wrote a famous book on skin
grafting titled De curtorum chirurgia per insitionem. His
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