Untitled - D Ank Unlimited

hypereosinophilia 346 hypersensitivity
endothelial cells expressing glycolipid and glycoprotein
galactose-α (1-3) galactose.
hypereosinophilia
Markedly elevated numbers of eosinophils in the peripheral
blood.
hypergammaglobulinemia
Elevated serum γ globulin (immunoglobulin) levels. A
polyclonal increase in immunoglobulins in the serum
occurs in any condition involving continuous stimulation
of the immune system, such as chronic infection, autoimmune
disease, systemic lupus erythematosus (SLE), etc.
Hypergammaglobulinemia may also result from a monoclonal
increase in immunoglobulin production, as in multiple
myeloma, Waldenström’s macroglobulinemia, and other
conditions associated with the formation of monoclonal
immunoglobulins. Repeated immunization may also induce
hypergammaglobulinemia.
hypergammaglobulinemic purpura
Purpura hyperglobulinemia.
hyper-IgD with periodic fever syndrome
An autoinflammatory primary immunodeficiency associated
with increased serum IgD. Attributable to mutations in
mevalonate kinase, an enzyme that participates in cholesterol
biosynthesis.
hyper-IgE syndrome
A primary immunodeficiency of unknown etiology and associated
with remarkably elevated circulating levels of IgE.
hyper-IgM syndrome (HIGM)
Related primary immunodeficiencies associated with normal
to markedly elevated levels of circulating IgM but very
diminished or absent levels of the remaining immunoglobulin
isotypes. Monoclonal antibodies against CD40 surface
protein of B cells induce isotype switching in the presence
of appropriate costimulatory cytokines. CD40L is a surface
molecule transiently expressed on activated T cells mostly
of the CD4 + subpopulation. Mutations of CD40L account
for the X-linked form of the disease.
hyperimmune
A descriptor for an animal with a high level of immunity
that is induced by repeated immunization of the animal to
generate large amounts of functionally effective antibodies,
in comparison to animals subjected to routine immunization
protocols, perhaps with fewer boosters.
hyperimmunization
Successive administration of an immunogen to an animal
to induce the synthesis of antibody in relatively large
amounts. This procedure is followed in the preparation of
therapeutic antisera by repeatedly immunizing animals to
render them hyperimmune.
hyperimmunized individual
A person who has formed alloantibodies against an antigen
to which he or she was previously exposed, such as a prior
allograft, blood transfusion, or pregnancy. May sometimes
be attributable to natural antibodies specific for antigenic
determinants of pathogens that cross react with allogeneic
donor antigens of a graft.
hyperimmunoglobulin E syndrome (HIE)
A condition characterized by markedly elevated immunoglobulin
E (IgE) levels (above 5000 IU/mL). The patients
have early eczema and repeated abscesses of the skin,
sinuses, lungs, eyes, and ears. Staphylococcus aureus,
Candida albicans, Haemophilus influenzae, Streptococcus
pneumoniae, and group A hemolytic streptococci are
among the more common infectious agents. The principal
infection produced by S. aureus and C. albicans is a “cold
abscess” of the skin. The failure of IgE to fix complement
and therefore cause inflammation at the infection site is
characteristic. IgG antibodies against IgE form complexes
that bind to mononuclear phagocytes, resulting in monokine
release that induces calcium resorption from bone. As calcium
is lost from the bone, osteoporosis results, leading to
bone fractures. Patients with HIE have diminished antibody
responses to vaccines and to major histocompatibility antigens.
They may be anergic, and in vitro challenge of their
lymphocytes with mitogens or antigens leads to diminished
responsiveness. The CD8 + T lymphocyte population in the
peripheral blood also decreases. The disease becomes manifest
in young infants, shows no predilection for males versus
females, and is not hereditary. Also called Job’s syndrome.
hyperimmunoglobulin M syndrome
An immunodeficiency disorder in which the serum
immunoglobulin M (IgM) level is normal or elevated. By
contrast, the serum IgG and IgA levels are strikingly diminished
or absent. Patients have repeated infections and may
develop neoplasms in childhood. This syndrome may be
transmitted in an X-linked or autosomal-dominant fashion.
It may also be related to congenital rubella. The condition
is produced by failure of T lymphocytes to signal IgMsynthesizing
B cells to switch to IgG- and IgA-producing
cells. In this X-linked disease in boys who are unable to
synthesize immunoglobulin isotypes other than IgM, the
gene encoding the CD40 ligand is defective. The T H cells
fail to express CD40L. These patients do not develop
germinal centers or displaced somatic hypermutation. They
do not form memory B cells and are subject to pyogenic
bacterial and protozoal infections.
hyperplasia
An increase in the cell number that leads to an increase in
organ size. It is often linked to a physiological reaction to a
stimulus and is reversible.
hypersensitive response (HR)
An antipathogen response in plants produced by avr-R
system activation that leads to alterations in Ca + flux,
MAPK activation, and NO and ROI formation. There is
rapid necrosis of plant cells in contact with the pathogen.
This process prevents spread of the pathogen and releases
hydrolytic enzymes that facilitate injury to the pathogen’s
structural integrity.
hypersensitivity
Increased reactivity or increased sensitivity by an animal
body to an antigen to which it has been previously
exposed. The term is often used as a synonym for allergy,
which describes a state of altered reactivity to an antigen.
Hypersensitivity has been divided into categories based
upon whether it can be passively transferred by antibodies
or by specifically immune lymphoid cells. The most widely
adopted current classification is that of Coombs and Gell,
which designates immunoglobulin-mediated hypersensitivity
reactions as types I, II, and III and lymphoid-cellmediated
(delayed-type) hypersensitivity/cell-mediated
immunity as a type IV reaction. Hypersensitivity generally
represents the “dark side,” signifying the undesirable
aspects of an immune reaction, whereas immunity implies a
desirable effect.