Untitled - D Ank Unlimited

unidentified reading frame (URF) 733 urushiols
immunoglobulin transport takes place across the placenta.
The colostrum contains very high levels of IgG 1 and very
little IgA. The IgA in milk is derived from the plasma.
A biliary pump removes IgA from serum for delivery by
way of the bowel to the gut lumen. Whereas immunologic
tissues are well developed before birth, differentiation of
peripheral organs does not occur until antigenic stimulation
occurs in extrauterine life. This antigenic stimulation
is followed by the development of follicles and germinal
centers. Because ungulates do not receive immunoglobulin
prenatally from their mothers, they are born agammaglobulinemic.
However, large amounts of maternal IgG are
concentrated in mammary glands just prior to parturition
and are ingested and absorbed intact into the circulation by
suckling neonates. In addition to antibodies in the colostrum
that are transferred to neonates, cells and other soluble
factors in milk are also important in passive protection.
unidentified reading frame (URF)
An open reading frame (ORF) that does not correlate with a
defined protein.
unitarian hypothesis
The view that one type of antibody produced in response to
an injection of antigen may induce agglutination, complement
fixation, precipitation, and lysis based on the type of
ligand with which it interacted. This contrasts with the earlier
belief that separate antibodies accounted for every type
of serological reactivity described above. Usually, more
than one class of immunoglobulin may manifest a particular
serological reactivity such as precipitation.
univalent
A single binding site.
univalent antibody
An antibody molecule with one antigen-binding site. Although
incapable of leading to precipitation or agglutination, univalent
antibodies or Fab fragments resulting from papain
digestion of an immunoglobulin G (IgG) molecule may block
precipitation of antigen by a typical bivalent antibody.
universal donor
A blood group O RhD – individual whose erythrocytes
express neither A nor B surface antigens. These red
blood cell fail to elicit hemolytic transfusion reactions in
recipients with A, B, AB, or O blood groups. However,
group O individuals serving as universal donors may
express other blood group antigens on their erythrocytes
that will induce hemolysis. It is preferable to use typespecific
blood for transfusions, except during disasters or
emergencies.
universal recipient
An ABO blood group individual whose cells express
antigens A and B and serum does not contain anti-A and
anti-B antibodies. Thus, red blood cells containing any of
the ABO antigens may be transfused to these individuals
without inducing a hemolytic transfusion reaction (i.e.,
from an individual with type A, B, AB, or O). It is best if a
universal recipient is Rh + (has the RhD antigen on erythrocytes)
to avoid a hemolytic transfusion reaction; however,
blood group systems other than ABO may induce hemolytic
reactions in universal recipients. Thus, it is best to use typespecific
blood for transfusions.
unprimed
Animals or cells that have had no previous contact with a
particular antigen.
unproductive rearrangements
DNA rearrangements of T cell receptor and immunoglobulin
genes that produce a gene incapable of encoding a
functional polypeptide chain.
unresponsiveness
The failure to respond to an immunogenic (antigenic) stimulus.
Unresponsiveness may be antigen-specific as in immunological
tolerance or nonspecific as a consequence of general
suppression of the immune system by whole-body irradiation
or immunosuppressive drugs such as cyclosporine.
uromodulin Tamm–Horsfall protein
An 85-kDa α 1 acid glycoprotein produced in Henle’s
ascending loop and distal convoluted tubules by epithelial
cells. It is a powerful immunosuppressive protein based
upon N-linked carbohydrate residues. It inhibits proliferation
of T cells induced by antigen and monocyte cytotoxicity.
Uromodulin is a ligand for interleukin-1α (IL1α), IL1β,
and tumor necrosis factor (TNF).
Uropod.
uropod
Lymphocyte cytoplasm extending as an elongated tail or
pseudopod in locomotion. A uropod may resemble the handle
of a hand mirror. The plasma membrane covers its cytoplasm.
urticaria
Pruritic skin rash identified by localized elevated, edematous,
erythematous, and itching wheals with pale centers
encircled by red flares. It is due to the release of histamine
and other vasoactive substances from mast cell cytoplasmic
granules arising from immunologic sensitization or physical
or chemical factors. It is a form of type I immediate hypersensitivity
mediated by immunoglobulin E (IgE) antibodies
in humans. The action of allergen or antigen with IgE
antibodies anchored to mast cells may lead to this form of
cutaneous anaphylaxis or hives. The wheal is due to leakage
of plasma from venules; the flare is caused by neurotransmitters.
Also called hives.
urushiols
Catechols of poison (Rhus toxicodendron) plants that act as
allergens to produce contact hypersensitivity (i.e., contact
dermatitis at skin sites touched by urushiol-bearing plants).
U