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cobra venom factor (CVF) 181 coelomocyte
vesicles convey receptor–macromolecule complexes from
extracellular to intracellular locations. Clathrin-coated
vesicles convey proteins from one intracellular organelle to
another. Refer also to coated pit.
cobra venom factor (CVF)
A protein in the venom of the Indian cobra, Naja naja. It
is the equivalent of mammalian C3b and thus can activate
the alternative pathway of complement. Mammalian factor
I does not inactivate cobra venom, which leads to the
production of a stable alternative pathway C3 convertase
if CVF is injected intravenously into a mammal. Thus, the
injection of cobra venom factor into mammals has been
used to destroy complement activity for experimental purposes.
A component of cobra venom interacts specifically
with the serum complement system, leading to its continuous
activation. CVF is a structural and functional analog
of complement component C3. It has been employed
to decomplement laboratory animals to investigate the
biological functions of complement. It has been used in
animal experiments involving xenotransplantation to show
that complement is a principal contributor to hyperacute
rejection of a transplanted organ. It has also been used
in antibody conjugates to render monoclonal antibodies
cytotoxic.
Arthur Fernandez Coca.
Coca, Arthur Fernandez (1875–1959)
American allergist and immunologist. He was a major force
in allergy and immunology. He named atopic antibodies
and was a pioneer in the isolation of allergens. He and
Robert A. Cooke classified allergies in humans.
co-capping
If two molecules are associated in a membrane, capping
of one induced by its ligand may lead also to capping
of the associated molecule. Antibodies to membrane
molecule x may induce capping of membrane molecule
y and x if x and y are associated in the membrane. In
this example, the capping of the associated y molecule is
termed co-capping.
Coccidioides immunity
Immunity against Coccidioides immitis depends upon T
lymphocytes. IFN-γ plays an important role in protection
conferred by the recombinant form of this cytokine in
experimental mice. Monocytes have a precise role in limiting
infection before a specific immune response develops.
Spherules and arthroconidia induce the synthesis of TNFα
by human monocytes in vitro. TNFα alone or combined
with IFN-γ promotes killing of spherules by human
monocytes in vitro. TNFα and IL6 levels have been shown
to be elevated in patients with overwhelming infections
by this organism. Antigen overload, specific suppressor T
lymphocyte activity from a circulating humoral suppressor
substance, may sometimes suppress the T lymphocyte A
Coccidioides-specific responses in some patients. A positive
skin test indicates previous infection. Results usually
remain positive for the patient’s lifetime. Of all infected
individuals, 90% develop antibody responses to C. immitis.
Mycelial phase antigens are most often used in serodiagnosis.
Immunoglobulin M (IgM) forms early but disappears
after 6 months, whereas IgG elevated titers may indicate
dissemination.
coccidioidin
A Coccidioides immitis culture extract used in a skin test
for cell-mediated immunity against the microorganism in a
manner analogous to the tuberculin skin test.
coccidiosis immunity
Immunity induced by infection is species- and in some
instances strain-specific, yet immunization with purified
antigens may induce heterologous protection. Immunity is
mediated by T cells and is far more significant to resistance
than the humoral immune response that is also stimulated.
Antibodies act mainly against extracellular parasites to reduce
invasion. CD4 + T cells control primary infections, whereas
CD8 + lymphocytes are more significant in later stages of
infection. There is a vaccine for chickens, but it is expensive.
coding joint
A structure formed when a V gene segment joins imprecisely
to a (D)J gene segment in immunoglobulin or T cell
receptor genes.
codominant
The expression of both alleles of a pair in a heterozygote.
The traits they determine are codominant as in the expression
of blood group A and B epitopes in type AB persons.
codominantly expressed
Gene expression when both alleles at one locus are expressed
in approximately equal amounts in heterzygotes. The highly
polymorphic major histocompatibility complex (MHC)
genes, as well as most other genes, manifest this property.
codon
A three-adjacent nucleotide sequence mRNA that acts as a
coding unit for a specific amino acid during protein synthesis.
The codon controls which amino acid is incorporated
into the protein molecule at a certain position in the polypeptide
chain. Of 64 codons, 61 encode amino acids, and 3
act as termination codons.
coelomate
An animal possessing a body cavity.
coelomocyte
A circulating or fixed ameboid phagocytic leukocyte that
participates in the defense of invertebrate animals that have
coeloms by phagocytosis and encapsulation.
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