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high endothelial postcapillary venules 325 hinge region
substance is a polysaccharide to immunocompetent adult
animals. Although no precise inducing dose of antigen can
be defined, usually in high-dose tolerance the antigen level
exceeds 10 4 mol antigen per kilogram of body weight. Also
called high-zone tolerance.
high endothelial postcapillary venules
Lymphoid organ vessels that are especially designed for
circulating lymphocytes to gain access into the parenchyma
of an organ. They contain cuboidal endothelium that permits
lymphocytes to pass between the cells into the tissues.
Lymphocyte recirculation from the blood to the lymph
occurs through these vessel walls.
High
endothelial
venule
(HEV)
Vein
Clathrin
Anti-gp330 IgG
High endothelial venules (HEVs).
Coated pit
gp330
high endothelial venules (HEVs)
Postcapillary venules of lymph node paracortical areas.
They also occur in Peyer’s patches that are components of
gut-associated lymphoid tissue (GALT). Their specialized
columnar cells bear receptors for antigen-primed lymphocytes.
They signal lymphocytes to leave the peripheral
blood circulation. These cuboidal cells express adhesion
molecules that promote adherence and transendothelial passage
of naïve lymphocytes. A homing receptor for circulating
lymphocytes is found in lymph nodes.
high responder
A mouse, guinea pig, or other inbred strain that mounts
pronounced immune responses to selected antigens in comparison
to the responses of other strains including so-called
low responder strains. Immune response (IR) genes encode
this capability.
Heymann’s glomerulonephritis.
high titer, low avidity antibodies (HTLAs)
Antibodies that induce erythrocyte agglutination at high dilutions
in the Coombs’ antiglobulin test. These antibodies cause
only weak agglutination and are almost never linked to hemolysis
of clinical importance. Examples of HTLA antibodies are
anti-Bg a , -Cs, -Ch, -Kna, -JMH, -Rg, and -Yk, among others.
high-zone tolerance
Antigen-induced specific immunosuppression with relatively
large doses of protein antigens (tolerogens). B cell
tolerance usually requires high antigen doses. High-zone
tolerance is relatively short lived. Called also high-dose
tolerance. Refer to high-dose tolerance.
higher vertebrates
Animals with backbones, including the agnatha (jawless fish
such as lampreys); Chondrichthyes (cartilaginous jawed fish
such as skates, sharks and rays); Osteichthyes (bony jawed
fish including lobe-finned, ray-finned, and advanced bony
fishes such as salmon); amphibians (frogs, toads, and salamanders);
reptiles (crocodiles and snakes); birds; and mammals
that include such divergent species as mice and humans.
highly active antiretroviral therapy (HAART)
The combined use of reverse transcriptase inhibitors and
a viral protease inhibitor for HIV infection. This therapy
can diminish virus titers to undetectable levels for more
than a year and slow the progression of HIV disease. The
combination slows the development of drug-resistant mutant
viruses that arise when a lone drug is used.
highly polymorphic
Units of inheritance (i.e., genes) possessing numerous alleles
for which most subjects in a population are heterozygous.
hinge region
An area of an immunoglobulin heavy chain situated
between the first constant domain and the second constant
domain (C H1 and C H2) in an immunoglobulin (Ig) polypeptide
chain. The high content of proline residues in this
region provides considerable flexibility to this area, which
enables the Fab region of an immunoglobulin molecule to
combine with cell surface epitopes it might not otherwise
reach. Fab regions of an Ig molecule can rotate on the hinge
region. The angle between the two Fab regions of an IgG
molecule may extend up to 180°. In addition to the proline
residues, one or several half cysteines may be associated
with the interchain disulfide bonds. Enzyme action by
papain or pepsin occurs near the hinge region. Whereas γ,
α, and δ chains contain hinge regions, μ and ε chains do
not. The 5′ part of the C H2 exon encodes the human and
H