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arcitumomab 77 Arthus, Nicolas Maurice (1862–1945)
uptake, and enhanced binding to endothelial cells. It can cause
cation fluxes, augment cytoplasmic calcium concentrations,
form intracellular pools, and activate phosphatidylinositol
hydrolysis. LTB 4 can act synergistically with prostaglandins
E 1 (PGE 1) and PGE 2 to induce macromolecule leakage in the
skin through increased vascular permeability. When injected
into the skin of a guinea pig, it can induce leukocytoclastic
vasculitis. Human polymorphonuclear neutrophils have two
sets of plasma membrane receptors. A high affinity receptor
set mediates aggregation, chemokinesis, and increased surface
adherence, whereas the low affinity receptor set mediates
degranulation and increased oxidative metabolism. A fraction
of CD4 + and CD8 + T lymphocytes bind LTB 4, but LTB 4 receptors
on lymphocytes remain to be characterized.
arcitumomab
A murine F(ab′) 2 fragment of an anti-carcinoembryonic
antigen (CEA) antibody labeled with technetium 99m
( 99m Tc) used for imaging patients with metastatic colorectal
cancer by immunoscintigraphy to evaluate spread of the
disease. Use of the F(ab′) 2 fragment diminishes the immunogenicity,
permitting it to be used more than once.
arenavirus immunity
Even though arenaviruses may not cause ill effects in carrier
rodents, when transmitted to primates they may induce
severe encephalitis, hepatitis, or hemorrhagic syndrome.
LCMV is a classic member of this group and has been
used to investigate virus-induced, cell-mediated immunity.
Infection of mice may be either acute (inducing strong
cell-mediated immunity) or persistent (associated with little
cell-mediated immunity). The immune response to the acute
infection either kills the mouse by causing meningitis or subsides
and renders the mouse LCMV-immune. CD8+ T cells
clear the virus infection and may also mediate pathological
changes of choriomeningitis when injected intracerebrally.
LCMV infection induces interferon γ (IFN-γ) and tumor
necrosis factor α, which affect host immune responses.
IFN-γ induces natural killer (NK) cell proliferation, which
eliminates pathogen-infected cells and selected tumors.
Arenaviruses persist in long-term carriers through antigenic
variation that evades the host immune response. Mice may be
protected from lethal LCMV challenge by peptide vaccination
or by vaccinia vectors that express viral epitopes.
arginine and immunity
Arginine, a dibasic nitrogen-rich amino acid, has a marked
immunomodulatory function. It is critical for the maintenance
of nitrogen balance and physiologic functions in humans.
Supplemental administration of arginine in experimental
animals led to increased thymic size, lymphocyte count, and
lymphocyte mitogenic response to mitogens and antigens. IL-2
synthesis is enhanced. Arginine protects against post-traumatic
thymic involution and the impairment of T cell function.
It enhances delayed-type hypersensitivity reactions in animal
studies and also promotes host antitumor responses. Arginine
is essential for the functions of various immunoregulatory proteins
including thymosin, thymopentin, and tuftsin. Arginine
exerts powerful effects on numerous cells and molecules of the
immune system and may have potential as a pharmacologic
agent in the treatment of immunocompromised patients.
Arlacel A ®
A mannide monooleate used as an emulsifier to stabilize
water-in-oil emulsions employed as adjuvants (e.g., Freund’s
adjuvant) in experimental immunology.
armed cytotoxic T lymphocyte (armed CTL)
A mature effector cytotoxic T lymphocyte that forms
chemical mediators prior to contact with antigen that will
be employed to fatally injure target cells with which they
come into contact.
armed effector T cells
Activated effector T cells induced to mediate their effector
functions as soon as they contact cells expressing the peptide–major
histocompatability complex (MHC) for which
they are specific. By contrast, memory T lymphocytes
require activation by antigen-presenting cells to empower
them to carry out effector functions.
armed macrophages
Macrophages bearing surface immunoglobulin G (IgG) or
IgM cytophilic antibodies or T cell lymphokines that render
them capable of inducing antigen-specific cytotoxicity.
Svante Arrhenius (left) and Paul Ehrlich (right).
armed mast cell
A mast cell whose Fcε receptors have bound IgE molecules
specific for antigen prior to interaction with that same allergen.
Arrhenius, Svante (1859–1927)
Arrhenius coined the immunochemistry term and hypothesized
that antigen–antibody complexes are reversible. He
was awarded the Nobel Prize for chemistry in 1903. (See
Arrhenius, S., Immunochemistry, Macmillan Publishers,
New York, 1907).
Artemis SCID
A form of severe combined immunodeficiency attributable
to mutations of the Artemis gene that codes for a factor
significant in both V(D)J recombination and DNA repair.
arthritis
Joint inflammation.
Arthus, Nicolas Maurice (1862–1945)
Paris physician who studied venoms and their physiological
effects; first to describe local anaphylaxis or the Arthus reaction
(1903). Author of De l’Anaphylaxie a l’Immunite, 1921.
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