Untitled - D Ank Unlimited

dinitrochlorobenzene (DNCB) 229 diphtheria toxin
dinitrochlorobenzene (DNCB)
A substance employed to test capacity to develop a cellmediated
immune reaction. A solution of DNCB is applied
to the skin of an individual not previously sensitized
against this chemical, where it acts as a hapten, interacting
with proteins of the skin. Re-exposure of this same individual
to a second application of DNCB 2 weeks after the
first challenge results in a T-cell-mediated, delayed-type
hypersensitivity (contact dermatitis) reaction. Persons with
impaired delayed-type hypersensitivity or cell-mediated
immunity may reveal impaired responses. The 2,4-dinitro-
1-chlorobenzene interacts with free α amino terminal
groups in polypeptide chains and with side chains of
lysine, tyrosine, histidine, cysteine, or other amino acid
residues.
dinitrofluorobenzene (2,4-dinitro-1-fluorobenzene)(DNFB)
A chemical employed to prepare hapten–carrier conjugates.
It inserts the 2,4-dinitrophenyl group into molecules containing
free –NH 2 groups. When placed on the skin, it leads
to contact hypersensitivity.
dinitrophenyl (DNP) group
Designation for 2,4-dinitrophenyl groups that become
haptens after they are chemically linked to –NH 2 groups
of proteins that interact with chlorodinitrobenzene, 2,4dinitrobenzene
sulphonic acid, or dinitrofluorobenzene.
These protein carrier–DNP hapten antigens are useful
as experimental immunogens. Antibodies specific for
the DNP hapten that are generated through immunization
with the carrier–hapten complex interact with
low molecular weight substances that contain the DNP
groups.
diphtheria and tetanus toxoids (adsorbed, injection)
The preparation intended for pediatric use (DT) is indicated
for active immunization against diphtheria and tetanus in
infants and children from 2 months to 7 years of age, for
whom the use of combined vaccine containing pertussis
antigen is contraindicated. The vaccine should be administered
intramuscularly. The potency of tetanus and diphtheria
toxoids has been determined based on immunogenicity
studies, with comparison to a serological correlate of protection
(0.01 antitoxin units/mL) established by the Panel
on Review of Bacterial Vaccines and Toxoids. Results of
the study indicated protective levels of antibody were raised
in more than 90% of the study population after primary
immunization with both components. Booster injections
were effective in 100% of individuals with pre-existing
antibody responses.
diphtheria and tetanus toxoids and acellular pertussis
vaccine (adsorbed [DTaP], injection)
Intended for active immunization against diphtheria, tetanus
and pertussis simultaneously in infants and children
6 weeks to 7 years of age (prior to seventh birthday).
These preparations combine diphtheria and tetanus toxoids
with acellular pertussis bacterial vaccine. The acellular
pertussis antigens include pertussis toxin (PT), FHA,
and pertactin. Immunization with diphtheria and tetanus
toxoid is believed to confer protection lasting 10 years.
Nevertheless, diphtheria toxoid does not prevent carriage
of Corynebacterium diphtheriae in the pharynx, nose, or
skin. Protection against pertussis lasts 4 to 6 years. Serum
diphtheria and tetanus antitoxin levels of 0.l IU/mL and
higher are considered protective. Efficacy of the pertussis
component does not have a well established correlate of
protection.
diphtheria antitoxin
An antibody generated by the hyperimmunization of
horses against Corynebacterium diphtheriae exotoxin
with injections of diphtheria toxoid and diphtheria toxins.
When used earlier in the 20th century to treat children
with diphtheria, many of the recipients developed serum
sickness. It may be employed for passive immunization to
treat diphtheria or for short-term protection during epidemics.
Presently, pepsin digestion of the serum globulin
fraction of the antitoxin yields F(ab′) 2 fragments of antibodies
that retain their antigen-binding property but lose
the highly antigenic Fc region. This process diminishes
the development of serum sickness-type reactions and is
called despecification.
diphtheria immunization
The repeated administration of diphtheria toxoids as alumprecipitated
toxoids (APTs). Toxoid–antitoxin floccules
(TAFs) constitute an alternate form for adults who show
adverse reactions to adenosine triphosphate (APT). Besides
this active immunization procedure, diphtheria antitoxin
can also be given for passive immunization in the treatment
of diphtheria.
diphtheria toxin
A 62-kDa protein exotoxin synthesized and secreted by
Corynebacterium diphtheriae. The exotoxin, which is distributed
in the blood, induces neuropathy and myocarditis
in humans. Tryptic enzymes nick the single-chain diphtheria
toxin. Thiols reduce the toxin to produce two fragments.
The 40-kDa B fragment gains access to cells through their
membranes, permitting the 21-kDa A fragments to enter.
Whereas the B fragment is not toxic, the A fragment is
toxic and it inactivates elongation factor 2, thereby blocking
eukaryocytic protein synthesis. Guinea pigs are especially
sensitive to diphtheria toxin, which causes necrosis at injection
sites, hemorrhage of the adrenals, and other pathologic
consequences. Animal tests developed earlier in the century
consisted of intradermal inoculation of C. diphtheriae
suspensions into the skin of unprotected guinea pigs compared
to a control guinea pig that had been pretreated with
passive administration of diphtheria antitoxin for protection.
In later years, toxin generation was demonstrated in
vitro by placing filter paper impregnated with antitoxin at
right angles to streaks of C. diphtheriae microorganisms
growing on media in Petri plates. Formalin treatment or
storage converts the labile diphtheria toxin into toxoid. A
secretory product of Corynebacterium diphtheriae, the
etiologic agent of diphtheria, produces symptoms of the
disease. Immunization requires the use of an inactive form
of the toxin (diphtheria toxoid). Refer to diphtheria toxin
and diphtheria toxoid.
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