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heterophile antigen 324 high-dose tolerance
unrelated species. The antibody is often an immunoglobulin
M (IgM) agglutinin. Heterophile antibodies are detected
in infectious mononucleosis patients who demonstrate
antibodies reactive with sheep erythrocytes. To differentiate
this condition from serum sickness, which also is associated
with high titers of heterophile antibodies, the serum
sample is absorbed with beef erythrocytes that contain
Forssman antigen. This treatment removes the heterophile
antibody reactivity from the sera of infectious mononucleosis
patients.
heterophile antigen
An antigen (epitope) present in divergent animal species,
plants, and bacteria that manifests broad cross reactivity
with antibodies of the heterophile group. Heterophile
antigens induce the formation of heterophile antibodies
when introduced into a species in which they are absent.
Heterophile antigens are often carbohydrates.
heterospecific
Showing specificity for a species other than the one from
which the substance in question was derived.
heterotopic
The placement of an organ or tissue graft in an anatomic
site other than the one where it is normally located.
heterotopic graft
A tissue or organ transplanted to an anatomic site other
than the one where it is usually found under natural
conditions—for example, the anastomosis of the renal
vasculature at an anatomical site that would situate the
kidney in a place other than the renal fossa, where it is
customarily found.
heterotypic vaccine
Refer to heterologous vaccine.
heterozygosity
The presence of different alleles at one or more loci on
homologous chromosomes.
heterozygous
Descriptor for individuals possessing two different alleles
of a particular gene.
HEV
Refer to high endothelial venules.
Hewson, William (1739–1774)
British physician credited as the “father of hematology.”
Heymann antigen
A 330-kDa glycoprotein (GP330) present on visceral
epithelial cell basal surfaces in coated pits and on tubular
brush borders. It participates in production of experimental
nephritis in rats. See also Heymann glomerulonephritis.
Heymann glomerulonephritis
An experimental model of membranous glomerulonephritis
induced by immunizing rats with proximal tubule
brush border preparations containing subepithelial antigen
or Heymann factor, a 330-kDa protein incorporated in
Freund’s adjuvant. The rats produce antibodies against
brush border antigens and membranous glomerulonephritis
is induced. Autoantibodies combine with shed epithelial
cell antigen. The union of antibody with Heymann antigen,
distributed in an interrupted manner along visceral epithelial
cell surfaces, leads to subepithelial electron-dense,
granular deposits. Immunoglobulins and complement are
deposited in a granular rather than linear pattern along the
glomerular basement membrane, as revealed by immunofluorescence.
The glomerulonephritis results from interaction
William Hewson.
of anti-brush border antibody with the 330-kDa glycoprotein,
which is fixed but discontinuously distributed on the
bases of visceral epithelial cells and is cross reactive with
brush border antigens. Heymann nephritis closely resembles
human membranous glomerulonephritis.
Heymann’s nephritis
Refer to Heymann glomerulonephritis.
HGG
Abbreviation for human γ globulin.
HGP-30
An experimental vaccine for AIDS that employs a synthetic
HIV core protein, p17.
HHV
Human herpesvirus.
Hib (Hemophilus influenzae type b)
A microorganism that induces infection, mostly in infants
below 5 years of age. Approximately 1,000 deaths among
20,000 annual cases are recorded. A polysaccharide vaccine
(Hib Vac) was of only marginal efficacy and poorly
immunogenic. By contrast, anti-Hib vaccine that contains
capsular polysaccharide of Hib bound covalently to a carrier
protein such as polyribosylribitol–diphtheria toxoid
(PRP-D) induces a very high level of protection, for example,
94% in one cohort of Finnish infants. PRP–tetanus
toxoid has induced 75% protection, and PRP–diphtheria
toxoid vaccine is claimed to be 88% effective.
hidden determinant
An epitope on a cell or molecule that is unavailable for interaction
with either lymphocyte receptors or the antigen-binding
region of antibody molecules because of stereochemical
factors. These hidden or cryptic determinants neither
react with lymphocyte or antibody receptors nor induce an
immune response unless an alteration in the steric configuration
of the molecule causes the epitope to be exposed.
HIG
Acronym for human immune globulin.
high-dose tolerance
Specific immunologic unresponsiveness induced by the
repeated administration of large doses of antigen (tolerogen)
if the substance is a protein or a massive single dose if the