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scurfy mouse 639 secondary granule
manifested as a wheal-and-flare reaction. This signifies that
the IgE antibodies are specific for the applied allergen and
lead to the degranulation of mast cells with release of pharmacologic
mediators of hypersensitivity such as histamine.
scurfy mouse
A natural mouse mutant that is a model of human IPEX
characterized by rough skin, runting, thrombocytopenia,
lymphadenopathy, and elevated susceptibility to infections.
A mutation of the FoxP3 gene encoding the scurfin transcription
factor leads to failure of T reg cells to function.
SDF-1
Stromal cell-derived factor 1 (SDF-1) is an α (CXC) family
chemokine. The stromal cell line PA6 synthesizes SDF-1,
which promotes proliferation of stromal cell-dependent
pre-B cells of the DW34 stromal cell-dependent pre-B cell
clone. Alternative splicing of the SDF-1 gene yields SDF-1α
and SDF-1β. SDF-1 is believed to be the natural ligand for
LESTR (leukocyte-derived seven-transmembrane domain
receptor). It is expressed by stromal cells, bone marrow,
liver tissue, and muscle.
SDS-PAGE
Polyacrylamide gel electrophoresis in sodium dodecyl sulfate.
Refer also to polyacrylamide gel electrophoresis.
SE
Abbreviation for staphylococcal enterotoxins.
second messengers (IP 3 and DAG)
Upon stimulation of the T cell receptor, protein tyrosine kinase
(PTK) becomes activated. PTK then phosphorylates phospholipase
C (PLC), which in turn hydrolyzes phosphatidylinositol
4,5-bisphosphate (PIP 2). The products of PIP 2 hydrolysis are
the intracellular second messengers, inositol 1,4,5-triphosphate
(IP 3) and 1,2-diacylglycerol (DAG). IP 3 leads to increased Ca 2+
release from intracellular stores, and DAG leads to increased
levels of protein kinase C. Protein kinase C and Ca 2+ signals,
such as the interaction of CA 2+ /calmodulin to activate calcineurin,
are associated with gene transcription and T cell activation.
Second messenger systems are also important in B cell activation
as a means of stimulating resting B cells to enter the cell
cycle. Through second messenger systems, extracellular signals
are received at cell membranes and relayed to nuclei to induce
responses at the genetic level.
second set rejection
Second set rejection of an organ or tissue graft by a host
who is already immune to the histocompatibility antigens of
the graft as a consequence of rejection of a previous transplant
of the same antigenic specificity as the second or as a
consequence of immunization against antigens of the donor
graft. The accelerated second set rejection compared to
rejection of a first graft is reminiscent of a classic secondary
or booster immune response.
second set response
The accelerated rejection of a second skin graft from a
donor that is the same or identical with the first donor. The
accelerated rejection is seen when regrafting is performed
12 to 80 days after rejection of the first graft. It is completed
in 7 to 8 days and is due to sensitization of the recipient by
the first graft.
second signal
The second of two signals required to activate lymphocytes.
Lymphocyte activation requires the recognition of antigen by
an antigen-specific leukocyte receptor in soluble form by the B
cell surface immunoglobulin receptor or complexed to a major
histocompatibility complex (MHC) molecule on an antigenpresenting
cell by the αβ heterodimer of the T cell receptor
(TCR) complex. Following this first signal, lymphocytes do not
become fully activated and are turned off, become unresponsive
to subsequent receptor stimulation, or undergo apoptosis.
A second signal is required to induce a productive immune
response. It enhances lymphocyte proliferation and promotes
cell survival and/or prevents lymphocyte receptor unresponsiveness.
Second signals may potentiate signals transduced by
TCR ligation and initiate enhanced proliferation. They may
facilitate antigen-driven lymphocyte proliferation and also
inhibit the induction of lymphocyte unresponsiveness and/
or programmed cell death. These latter costimulatory signals
activate intracellular pathways different from those induced by
the antigen–receptor complex. Different surface molecules can
provide second signals.
secondary allergen
An agent that induces allergic symptoms because of cross reactivity
with an allergen to which the individual is hypersensitive.
secondary antibody
An antibody directed against the Fc region of an unlabeled
primary antibody that has reacted with an antigen of interest.
Application of a labeled secondary antibody after washing
away unbound primary antibody permits the detection
of primary antibody–antigen complexes.
secondary antibody response
Immunoglobulin M (IgM) appears before IgG in the primary
antibody response. The inoculation of an immunogen into
an experimental animal primed by previous immunization
with the same immunogen produces antibodies following the
secondary immunogenic challenge that develop more rapidly,
last longer, and reach a higher titer than in the primary
response. Antibodies produced in the secondary response
are predominantly IgG and reach levels that are 10-fold or
greater than those in the primary antibody response.
secondary disease
A condition that occurs in irradiated animals whose cell populations
have been reconstituted with histoincompatible, immunologically
competent cells derived from allogeneic donor
animals. Ionizing radiation induces immunosuppression in the
recipients, rendering them incapable of rejecting the foreign
cells. Thus, a recipient has two cell populations, its own and the
introduced one. Thus, these animals are radiation chimeras.
After an initial period of recovery, they develop a secondary
runt disease that is usually fatal within 1 month.
secondary follicle
An area in a peripheral lymphoid organ where a germinal
center is located. Usually associated with a secondary
immune response more often than with a primary one.
It forms a ring of concentrically packed B lymphocytes
surrounding a germinal center. The infiltration of primary
follicles by activated T and B cells results in formation of
secondary follicles that lead to germinal centers and facilitation
of terminal differentiation of activated B cells into
memory B and plasma cells.
secondary granule
A structure in the cytoplasm of polymorphonuclear leukocytes
that contains vitamin B 12-binding protein, lysozyme,
and lactoferrin in neutrophils. Cationic peptides are present
in eosinophil secondary granules. Histamine, plateletactivating
factor, and heparin are present in the secondary
granules of basophils.
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