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T cell antigen-specific suppressor factor 683 T cell development
Plasma
membrane
Antigen binding site
α
β
T Cell receptor
heterodimer
γ
polypeptides. Each of the two polypeptides comprising each
receptor has a constant and a variable region (similar to
immunoglobulin). Reminiscent of the diversity of antibody
molecules, T cell antigen receptors can likewise identify a
tremendous number of antigenic specificities (estimated to
be able to recognize 10 15 epitopes). The TCR is comprised
of a minimum of seven receptor subunits whose production
is encoded by six separate genes. Following transcription,
these subunits are assembled precisely. Assimilation of the
complete receptor complex is requisite for surface expression
of TCR subunits. Numerous biochemical events are
associated with activation of a cell through a TCR. These
events ultimately lead to receptor subunit phosphorylation.
T cells may be activated by the interaction of antigen, in
the context of MHC, with the T cell receptor. This involves
transmission of a signal to the interior through the CD3
protein to activate the cell.
T cell antigen-specific suppressor factor
A soluble substance produced by a suppressor T cell after it
has been activated. This suppressor factor has been claimed
δ
CD3 Proteins
T cell antigen receptor.
Large
pre- B cell
Small
B cell
Intermediate
B cell
Mature
B cell
Immunoblast
ε
Early B
lineage
precursor
ζ ζ ζ
η
Lymphoid
stem cell
Active
B cell
to bind antigen and cause the immune response to be suppressed
in an antigen-specific manner.
T cell areas
Regions of secondary tissues occupied predominantly by
T lymphocytes.
T cell chemotactic factor
Former term for interleukin-8 (IL8).
T cell clonal expansion
Clonal expansion of T lymphocytes after initial encounter
with antigen is a critical mechanism of the effector limb of
the immune response. This permits the immune system to
respond to a broad spectrum of pathogens. Clonal expansion
is closely regulated to prevent inappropriate responses.
Increased clonal expansion is desirable during the early
course of an infection and in the prevention of growth and
survival of T cells mediating autoimmune disease.
T-cell-dependent (TD) antigen
An immunogen that is much more complex than the
T-cell-independent (TI) antigens. TD antigens are usually
proteins, protein–nuclear protein conjugates, glycoproteins,
or lipoproteins. They stimulate all five classes of
immunoglobulin, elicit anamnestic or memory responses,
and are present in most pathogenic microorganisms. These
properties ensure that an effective immune response can be
generated in a host infected with these pathogens.
T cell development
Stem cells in the bone marrow that are destined to develop
into T cells migrate to the thymus, where they undergo
maturation and development. These precursors of T cells
possess unrearranged T cell receptor (TCR) genes and do
not express CD4 or CD8 markers. Thymocytes (developing
T cells) are found first in the outer cortex, where their
numbers increase; the TCR genes are rearranged; and
CD3, CD4, CD8, and TCR molecules are expressed on
the surface. During maturation, these cells pass from the
CD4
Suppressor/
Inducer
T cell
Helper
T cell
Subcortical
thymocyte
Thymus cell differentation⎯T cell maturation.
CD8
Cytotoxic
T cell
Activated T cell
Suppressor
T cell
Bone marrow
Thymus
Blood
Lymph node
T