Untitled - D Ank Unlimited

Castleman’s disease 137 catalytic antibodies
Release of cytochrome c from the mitochondria can trigger a series of
events leading to the activation of effector caspases. For example, procaspase
9 is activated when complexed with dATP, APAF-1, and extramitochondrial
cytochrome c. Following activation, caspase 9 can inhibit
apoptosis by cleaving additional caspases.
Activation of procaspase 9 can occur upon formation of a complex with
Apaf-1 and cytochrome c. Caspase 9 may then activate additional caspases
through proteolytic cleavage (e.g. procaspases-3, -6, and -7).
with the cytoplasmic death domains of the receptor. Caspase
9 activates disassembly in response to agents or insults that
trigger release of cytochrome c from the mitochondria and is
activated when complexed with dATP, APAF-1, and extramitochondrial
cytochrome c. Caspase 3 appears to amplify caspase
8, and caspase 9 signals into a full-fledged commitment to
disassembly. Both caspase 8 and caspase 9 can activate caspase
3 by proteolytic cleavage, and caspase 3 may then cleave vital
cellular proteins or activate additional caspase by proteolytic
cleavage. Many other caspases have been described. Caspases
proteolytically disassemble cells. They are present in healthy
cells as inactive proforms. During apoptosis, most caspases
are activated by proteolytic cleavage. Caspase 9, however, may
be active without being proteolytically cleaved. Activation is
through autoproteolysis or cleavage by other caspases. Cleavage
of caspases generates a pro-domain fragment and subunits of
approximately 20 and 10 kDa. Active caspases appear to be
tetramers consisting of two identical 20-kDa subunits and two
identical 10-kDa subunits. Detection of either the 20- or 10-kDa
subunit by immunoblotting may imply activation of the caspase.
Colorimetric and fluorometric assays using fluorogenic peptide
substrates can be used to measure caspase activity in apoptotic
cells. Caspases cleave substrate proteins at the carboxyl termini
of specific aspartates. Tetrameric peptides with fluorometric or
colorimetric groups at the carboxyl terminal have been used
to determine the Km values of caspases. Although there is
preference for peptides with certain amino acid (aa) sequences,
the aa sequence may have some variance. Caspases also have
overlapping preferences for the tetrameric aa sequence (i.e., the
same substrates can be cleaved by multiple caspases although
one caspase may have a lower Km). Peptides containing groups
that form covalent bonds with the cysteine residing at the active
site of the caspase are often used to inhibit caspase activities.
Castleman’s disease
Also called giant lymph node hyperplasia. A disease of
unknown etiology that involves both lymph nodes and extra-
nodal tissues. Two histopathologic subtypes have been
described. The first, termed hyaline-vascular angiofollicular
lymph node hyperplasia, accounts for 90% of the cases. It usually
affects young men who present with an asymptomatic mass
in the mediastinum. Histopathologically, it reveals numerous
small, follicle-like structures, frequently with radially penetrating,
thick-walled, hyalinized vessels, concentrically arranged
small lymphocytes around the follicular structures, called
“onion skinning,” and extensive proliferation of capillaries
in the interfollicular areas. The second type of Castleman’s
disease is plasma cell angiofollicular lymph node hyperplasia,
which comprises 10% of the cases. It is either a localized mass
or a multicentered systemic disorder. The mass may consist
of multiple matted lymph nodes with histopathologic features
that include large hyperplastic follicles with fewer permanent
penetrating vessels than in the hyaline-vascular type, with
pronounced interfollicular plasma cytosis and permanent
vascularity. A multicentric type of the plasma cell variant
of angiofollicular lymph node hyperplasia is more aggressive.
Affected patients may have increased risk for developing
Kaposi’s sarcoma or immunoblastic lymphoma. Clinical
features of plasma cell angiofollicular hyperplasia include fever,
polyclonal hypergammaglobulinanemia, elevated sedimentation
rate, and anemia.
cat scratch disease
Regional lymphadenitis, common in children following
a cat scratch. The condition is induced by a small Gramnegative
bacillus. Erythematous papules may appear on
the hands or forearms at the site of the injury. Patients
may develop fever, malaise, swelling of the parotid gland,
lymphadenopathy that is regional or generalized, maculopapular
rash, anorexia, splenic enlargement, and encephalopathy.
Hyperplasia of lymphoid tissues, formation of
granulomas, and abscesses may occur. A positive skin test,
together with history, establishes the diagnosis. Gentamycin
and ciprofloxacin have been used in treatment.
catalase
An enzyme present in activated phagocytes that causes degradation
of hydrogen peroxide and superoxide dismutase.
catalytic antibodies
Antibodies that are exclusively specific for a particular ligand
and are also catalytic. Approximately 100 reactions have been
catalyzed by antibodies. Among these are pericyclic processes,
C