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diphtheria toxoid 230 direct tag assays
diphtheria toxoid
An immunizing preparation generated by formalin inactivation
of Corynebacterium diphtheriae exotoxins. This
toxoid, used in the active immunization of children against
diphtheria, is usually administered as a triple vaccine that
includes pertussis microorganisms and tetanus toxoid as a
purified toxoid absorbed to hydrated aluminum phosphate
(PTAP) or as an alum-precipitated toxoid (APT). Infants
immunized with one of these preparations develop active
immunity against diphtheria. Toxoid–antitoxin floccules
(TAFs) may be administered to adults who demonstrate
adverse hypersensitivity reactions to toxoids.
diphtheria vaccine
An immunizing preparation to protect against
Corynebacterium diphtheriae. Refer to DTaP vaccine.
diploid
A descriptor to indicate dual copies of each autosome and
two sex chromosomes in a cell nucleus. The diploid cell has
twice the number of chromosomes in a haploid cell.
direct agglutination
The aggregation of particulate antigens such as microorganisms,
red cells, or antigen-coated latex particles when they
react with specific antibody.
direct allorecognition
The process whereby the T cells of a transplant recipient
detect peptide/allo-MHC epitopes on allogeneic graft donor
cell surfaces. Refer to allorecognition.
direct amplicon analysis
A technique used in HLA tissue typing for the identification
of an unknown HLA allele through discovery of the
specific CR primers capable of amplifying a polymorphic
region of a gene. Gel electrophoresis and ethidium
bromide staining are used to detect the products of
amplification.
direct antigen presentation
Cell surface allogeneic major histocompatibility complex
(MHC) molecule presentation by graft cells to T lymphocytes
of the graft recipient leading to T lymphocyte
activation. No processing is required. Direct recognition
of foreign MHC molecules is a crossreaction between a
normal T cell receptor (TCR) that recognizes self MHC
molecules plus foreign antigen and the allogeneic MHC
molecule–peptide complex. The powerful T cell response to
allografts is due in part to direct presentation.
direct antiglobulin test
An assay in which washed erythrocytes are combined with
antiglobulin antibody. If the red cells had been coated with
nonagglutinating (incomplete) antibody in vivo, agglutination
would occur. Examples of this in humans include
hemolytic disease of the newborn in which maternal
antibodies coat the infant’s erythrocytes, and autoimmune
hemolytic anemia in which the subject’s red cells are coated
with autoantibodies. The coating is the basis of the direct
Coombs’ test.
direct Coombs’ test
Refer to direct antiglobulin test.
direct fluorescence antibody method
The use of polyclonal or monoclonal antibodies labeled
with a fluorochrome such as fluorescein isothiocyanate that
yields an apple-green color by immunofluorescence microscopy,
or rhodamine isothiocyanate that produces a reddishorange
color, to identify a specific antigen. This technique
Antigen
Autoantibody
Tissue
Fluorescent antihuman
gamma globulin
Direct fluorescence antibody technique.
is routinely used in immunofluorescence evaluation of renal
biopsy specimens and skin biopsy preparations to detect
immune complexes comprised of various immunoglobulin
classes or complement components.
direct immunofluorescence
The use of fluorochrome-labeled antibody to identify antigens,
especially those of tissues and cells. An example is the
immunofluorescence evaluation of renal biopsy specimens.
direct pathway of allorecognition
The process whereby a transplant recipient’s T cells are
stimulated by interactions of their receptors with the transplant
donor’s dendritic allogeneic HLA molecules.
direct reaction
Skin reaction caused by the intracutaneous injection of
viable or nonviable lymphocytes into a host that has been
sensitized against donor tissue antigens. This represents
a type IV hypersensitivity reaction, which is classified as
a delayed-type reaction mediated by T cells. Reactivity is
against lymphocyte surface epitopes.
direct staining
A version of the fluorescent antibody staining technique in
which a primary antibody has been conjugated with a fluorochrome
and applied directly to a tissue sample containing
the antigen in question.
direct tag assays
A method in which a tagged antigen or antibody is
employed to detect its untagged specific or complementary
antibody or antigen.