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soluble cytokine receptors 662 specific granule
soluble cytokine receptors
IL1 type I-R, IL1 type II-R, IL2Rα, IL2Rβ, IL4R,
IL5Rα, IL6Rα, gp130 IL6Rβ ciliary neurotrophic factor
(CNF)-Rα, and growth hormone R. Most of these function
by blocking ligand binding.
soluble liver antigen (cytokeratin autoantibodies)
Autoantibodies that react with liver but not kidney as
revealed by immunofluorescence. They are found in a subgroup
of patients with chronic autoimmune hepatitis (AIH)
with negative antinuclear antibodies (ANAs) and negative
liver–kidney microsome 1 (LKM-1) autoantibodies and a
low prevalence of autoantibodies against smooth muscle
mitochondria and liver membrane antigens. These autoantibodies
are believed to be identical to LP2 autoantibodies
present in 45% of patients with cryptogenic chronic active
hepatitis.
somatic
Pertaining to the body wall; of the body.
somatic antigen
An antigen, such as the O antigen, that is part of the structure
of a bacterial cell.
somatic cell hybrid
The union of two or more sets of chromosomes into a single
large nucleus as a consequence of fusion of multiple heterokaryon
nuclei.
somatic gene conversion
Nonreciprocal exchange of sequences between genes.
A portion of the donor gene or genes is copied into an
acceptor gene, leading to alteration only in the acceptor
gene. It serves as a mechanism to generate diverse immunoglobulins
in nonhuman species.
somatic gene therapy
A potential therapy to treat or cure inherited immunodeficiency
diseases. Stem cells derived from a patient are
transfected with a normal copy of the defective gene of the
patient. The stem cells now equipped with a good copy of
the defective gene are reinfused into the patient’s circulation.
somatic hybrid selection
Selection of somatic cell hybrids with required characteristics
by complementation.
somatic hypermutation
The induced increase in frequency of mutation in rearranged
variable region DNA of immunoglobulin genes
in activated B cells. The high frequency introduction of
single or double nucleotide substitutions into the V exons
of Ig genes, leading to elevated numbers of random point
mutations in the V regions of Ig proteins. This increase
leads to the synthesis of variant antibodies, some of which
have higher affinities for antigen. Somatic mutation may
occur in germinal centers. Only somatic cells are affected.
Somatic hypermutation is not inherited through germline
transmission. T cell receptor genes do not undergo somatic
hypermutation.
somatic mutation
A genetic variation in a somatic cell that is heritable by its
progeny. Increased somatic mutation enhances diversity of
the light and heavy chain variable regions of an antibody.
Immunoglobulin G (IgG) and IgA antibodies reveal somatic
mutations more often than IgM antibodies. Such a mutation
is a mechanism whereby point mutations can be introduced
into the rearranged immunoglobulin variable region genes
during B lymphocyte activation and proliferation.
somatic recombination
DNA recombination whereby functional genes encoding variable
regions of antigen receptors are produced during lymphocyte
development. A limited number of inherited or germline
DNA sequences that are first separated from each other are
assembled together by enzymatic deletion of intervening
sequences and relegation. This process takes place only in
developing B or T cells. Also called somatic rearrangement.
Gel with
separated
DNA fragments
Capillary action
Filter paper
Side view of setup
Southern blotting.
Nitrocellulose
Filter paper wick
Buffer
southern blotting
A procedure to identify DNA sequences. Following
extraction of DNA from cells, it is digested with restriction
endonucleases to cut the DNA at precise sites into
fragments. This is followed by separation of the DNA
segments according to size by electrophoresis in agarose
gel, denaturation with sodium hydroxide, and transfer of
the single-stranded DNA to a nitrocellulose membrane
by blotting. This procedure is followed by hybridization
with an 35 S- or 32 P-radiolabeled probe of complementary
DNA. Alternatively, a biotinylated probe may be used.
Autoradiography or substrate digestion identifies the location
of the DNA fragments that have hybridized with the
complementary DNA probe. Specific sequences in cloned
and in genomic DNA can be identified by southern blotting.
DNA analysis is referred to as a southern blot; RNA analysis
is referred to as a northern blot; and protein analysis is
referred to as a western blot. A northwestern blot is one in
which RNA–protein hybridizations are formed.
southwestern blot
A method that combines southern blotting to identify DNA
segments with western immunoblotting that characterizes
proteins. A protein may be hybridized to a molecule of
single-stranded DNA bound to a membrane. Southwestern
blotting is helpful in delineating nuclear-transcriptionrelated
proteins.
SP-40,40
A heterodimeric serum protein derived from soluble C5–C9
complexes that may modulate the cell lysing action of the
membrane attack complex (MAC).
spacer
Refer to the 12/23 rule.
species specificity
Cellular or tissue antigens present in one species only and
not found in other species.
specific granule
A secondary granule in the cytoplasms of polymorphonuclear
leukocytes that contains lysozyme, vitamin B 12binding
protein, neutral proteases, and lactoferrin. It is