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precipitation reaction 590 presentosome
Tube no.
Rabbit
antiserum
mg egg albumin
(antigen)
1 ml.
0.24
1 ml.
0.18
have the same antigenic determinants. If antibodies against
two unrelated antigen preparations are combined and placed
in the central well and their homologous antigens are placed
in separate adjacent peripheral wells, a line of precipitation
is produced by each antigen–antibody reaction to give the
appearance of crossed sword points. This constitutes a reaction
of nonidentity and implies that the antigenic determinants are
different in the two samples of antigen. A third pattern known
as a reaction of partial identity occurs when two antigen preparations
that are related but not the same are placed in separate
adjacent wells and an antibody preparation that cross reacts
with both is placed in a central well. The precipitation lines
between each antigen–antibody system converge, but a spur or
extension of one of the precipitation lines occurs. This reaction
of partial identity with spur formation implies that the antigen
preparations are similar, but that one of them has an antigenic
determinant not present in the other. A reaction of identity and
nonidentity may be observed simultaneously, implying that two
separate antigen preparations have both common and different
antigenic determinants.
precipitation reaction
Refer to precipitin test, precipitation, precipitation curve,
and precipitation in gel media.
precipitin
An antibody that interacts with a soluble antigen to yield
an aggregate of antigen and antibody molecules in a lattice
framework called a precipitate. Under appropriate conditions,
the majority of antibodies can act as precipitins.
precipitin reaction
Refer to precipitin test, precipitation, precipitation curve,
and precipitation in gel media.
precipitin reaction curve
Refer to precipitation curve.
precipitin test
An assay in which antibody interacts with soluble antigen in
the presence of electrolyte to produce a precipitate. Both qualitative
and quantitative precipitin reactions have been described.
preclinical trials
Assay for toxicity and teratogenicity of an agent or entity
in both nonhuman primates and nonprimate animals. May
also include efficacy testing.
prednisolone (1,4-pregnadiene-11β,17α, 21-triol-3,20-dione)
A semisynthetic steroid with glucocorticoid action. The
molecular configuration into which the immunosuppressive
prednisone drug is converted in vivo.
prednisone (1,4-pregnadiene-17α,21-diol-3,11,20-trione)
A synthetic steroid with glucocorticoid action. A powerful
anti-inflammatory and immunosuppressive agent used in
recipients of organ allotransplants.
1
2 3 4 5 6 7
1 ml.
0.12
1 ml.
0.09
Precipitation reaction in liquid media.
1 ml.
0.06
1 ml.
0.03
1 ml.
0.01
preemptive immunity
Resistance shown by virus-infected cells to superinfection
with a different virus.
pre-GC
Descriptor of a leukemia/lymphoma in which the transformed
cells express a naïve B cell phenotype. Somatic
mutations in the genome are rare.
preintegration complex
A configuration in the cytoplasm of the host cell that
possesses all the components of the HIV core with the
exception of the capsid. HIV RT synthesizes the viral DNA
rapidly within this configuration. The complex matrix proteins
then pilot it into the nucleus.
prekallikrein
A kallikrein precursor. The generation of kallikrein from
prekallikrein can activate the intrinsic mechanism of
blood coagulation.
premalignant clone
Genetically altered cell clone at a stage before malignant
conversion during the progression of carcinogenesis.
premunition
A type of protective immunity characterized by the
presence of a few pathogenic microorganisms of a
particular species remaining in the body, apparently
stimulating a protective immune response. Premunity
is associated with certain protozoal diseases such as
bovine babesiosis.
preneoplastic clone
A genetically altered cell clone at a stage before development
into a tumor during the progression of carcinogenesis.
preprogenitor cells
This pool of cells represents a second step in the maturation
of B cells and is induced by nonspecific environmental
stimuli. Preprogenitors are immature cells that are unable
to mount an immune response but constitute the pool from
which specific responsive clones will be selected by a
specific antigen. They are present in the bone marrow and
peripheral lymphoid organs such as the spleen where they
form a minor population. They are characterized by the
presence of some surface markers, frequently doublet or
triplet surface immunoglobulins, and are capable of stimulation
by selected activators. Sometimes termed B1 cells.
present
Refer to antigen presentation.
presentosome
A molecular assemblage on both sides of the endoplasmic
reticulum membrane that aids processing of endogenous
antigen. Proteasomal degradation yields peptides
that are complexed with HSP70, HSP90, or HSP 110 in