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chief cell autoantibodies 166 cholera toxin
chief cell autoantibodies
Antibodies reactive with chief cells that are principal
sources of PG1 (the main form of serum pepsinogen). They
are significantly diminished in atrophic gastritis type A,
which is associated with pernicious anemia. Autoantibodies
against pepsinogen, a 41-Kda antigen, are more frequent
in pernicious anemia than are intrinsic factor antibodies.
Pepsinogen autoantibodies are also present in approximately
50% of active duodenal ulcer patients, a quarter of
whom may have autoantibodies against H + /K + ATPase.
Chimera.
chimera
The presence in an individual of cells of more than one
genotype. This can occur rarely under natural circumstances
in dizygotic twins (such as in cattle) that share a
placenta in which the blood circulation has become fused,
causing the blood cells of each twin to circulate in the
other. More commonly, it refers to a human or other animal
that received a bone marrow transplant that provides a cell
population consisting of donor and self cells. Tetraparental
chimeras can be produced by experimental manipulation.
The name chimera derives from a monster of Greek mythology
that had the body of a goat, the head of a lion, and the
tail of a serpent.
chimeric antibodies
Antibodies that have, for example, mouse Fv fragments for
the Ag-binding portion of the molecule but Fc regions of
human immunoglobulin (Ig) that convey effector functions.
chimeric protein
A molecular structure comprised of segments of at least
two, or possibly more, different proteins.
chimerism
The presence of two genetically different cell populations
within an animal at the same time.
Chlamydia immunity
Chlamydiae infect many animal species and various
anatomical sites. No single pattern of host response can
be described, but similarities in effector mechanisms may
exist. The strain or serovar of the infecting microorganism
is also significant. In vitro studies and genital respiratory
and ocular animal models have provided most of the
information about both protective and pathologic host
responses. Acute inflammation is the initial response, with
participation by polymorphonuclear leukocytes (PMNs)
that may counteract the microorganisms but also cause
pathologic changes. When chlamydiae infect epithelial
cells, interleukin- (IL1) is released, as well as IL8, a potent
PMN chemoattractant. When these microorganisms
infect macrophages, lipopolysaccharide (LPS) triggers the
synthesis of TNFα, IL1, and IL6. They may also activate
the alternative pathway of complement. IL8, TNFα, and
complement may induce chemotaxis of PMNs to the local
site. ICAM-1, VCAM-1, and MAdCAM-1 are all detectable
early in the infection and may be addressins responsible for
PMN extravasation at sites of infection. Natural killer (NK)
cells may appear early after infection of the genital tract.
Chlamydial infection produces both humoral and cell-mediated
immune responses. Cell-mediated immunity has been
found important in both mouse and guinea pig models. The
CD4 + T cells are the main subset responsible for protective
cell-mediated immunity. In genital infections, the T H1
subset of CD4 T cells is the principal cell type leading to
the formation of high levels of IFN-γ, which is believed to
have a protective role. In some models, antibody appears to
be important in the resolution of infection. Antibody may
neutralize chlamydial elementary bodies in vitro. Immunity
to chlamydial infections is short lived. No effective vaccine
for chlamydia infections in humans currently exists, but a
veterinary vaccine is available.
HOOC CH2 CH2 CH2 N
CH 2 CH 2 Cl
CH2 CH2 Cl
Structure of chlorambucil (4-[bis (2-chloroethyl)] amino-phenylbutyric
acid).
chlorambucil (4-[bis(2-chloroethyl)]amino-phenylbutyric acid)
An alkylating and cytotoxic drug. Chlorambucil is not as
toxic as is cyclophosphamide and has served as an effective
therapy for selected immunological diseases such as
rheumatoid arthritis, systemic lupus erythematosus (SLE),
Wegener’s granulomatosis, essential cryoglobulinemia, and
cold agglutinin hemolytic anemia. Although it produces
bone marrow suppression, it has not produced hemorrhagic
cystitis and is less irritating to the gastrointestinal tract
than cyclophosphamide. Chlorambucil increases the likelihood
of opportunistic infections and the incidence of some
tumors.
chlorodinitrobenzene (1-chlor-2,4-dinitrobenzene)
More often termed dinitrochlorobenzene (DNCB). A
chemical substance used to test for a patient’s ability to
develop the type of delayed-type hypersensitivity referred to
as contact hypersensitivity. This is a type IV hypersensitivity
reaction. The chemical is applied to a patient’s forearm.
Following sufficient time for sensitization to develop, the
patient’s other forearm is exposed to a second (test) dose of
the same chemical. In an individual with an intact cellmediated
limb of the immune response, a positive reaction
develops at the second challenge site within 48 to 72 hours.
Individuals with cell-mediated immune deficiency disorders
fail to develop a positive delayed-type hypersensitivity
reaction.
cholera toxin
A Vibro cholerae enterotoxin comprised of five B subunits
that are cell-binding, 11.6-kDa structures that encircle a
27-kDa catalase that conveys ADP-ribose to G protein,
leading to continual adenyl cyclase activation. Other toxins