Untitled - D Ank Unlimited

Lewis blood group system 451 light chain
lewis Blood Group System
Genotype Secretor Status Phenotype
(a) Le, H, se Nonsecretor Lea+b–
(b) Le, H, Se Secretor Lea–b+
(a) le, H, se Nonsecretor Lea–b–
(a) le, H, Se Secretor Lea–b–
Lewis blood group system
An erythrocyte antigen system that differs from other red
cell groups in that the antigen is present in soluble form
in blood and saliva. Lewis antigens are adsorbed from the
plasma onto red cell membranes. The Lewis phenotype
expressed is based on whether the individual is a secretor
or nonsecretor of the Lewis gene product. Expression of the
Lewis phenotype is dependent also on the ABO phenotype.
Chemically, Lewis antigens are carbohydrates. Lewis secretors
face increased likelihood of urinary tract infections
induced by Escherichia coli and other microbes because
of the linkage of carbohydrate residues of glycolipids and
glycoproteins on urothelial cells.
Lewis x /sialyl-Lewis x; CD15/CD15S
The blood-group-related antigen Lewis x (Le x ) and related
oligosaccharide sequences on glycoproteins and glycolipids
serve as ligands for selectins, the leukocyte–endothelium
adhesion molecules critical to the early stages of leukocyte
recruitment in inflammation. Le x and sialyl-Lewis x
are human granulocyte and monocyte markers designated
CD15 and CD15s, respectively. Monocytes express mainly
the sialyl-Le x . Sialic acid masks the expression of Le x
antigen. Le x and sialyl-Le x are tumor-associated antigens.
The oligosaccharides may be inappropriately expressed
on tumor cells but are established as distinctive markers
of myeloid cells in human peripheral blood. Le x - and
Le a -related sequences serve as ligands for carbohydratebinding
receptors, the selectins. All three selectins bind to
sialyl-Le x -related sequences when they are exhibited in the
clustered state on protein or lipid. E-selectin also binds the
asialo-Le x sequence, but less avidly.
L f dose (historical)
The flocculating unit of diphtheria toxin; the amount of
toxin that flocculates most rapidly with one unit of antitoxin
in a series of mixtures containing constant amounts of
toxin and varying amounts of antitoxin. This unit must be
calculated.
L f flocculating unit (historical)
The flocculating unit of diphtheria toxin; the amount of
toxin that flocculates most rapidly with one unit of antitoxin
in a series of mixtures containing constant amounts of toxin
and varying amounts of antitoxin. Historically, a unit of
antitoxin was considered as the least quantity that would
neutralize 100 minimal lethal doses of toxin administered
to a guinea pig. Modern usage relates antitoxic activity to
an international standard antitoxin.
LFA-1, LFA-2, LFA-3
Refer to leukocyte-function-associated antigens.
LFA-1 deficiency
An immunodeficiency caused by a defect in lymphocyte
function-associated antigen, a 95-kDa β chain linked to
CD11a that ds natural killer (NK) cell binding, T helper
cell reactivity, and cytotoxic-T-cell-mediated killing.
This deficiency is associated with pyogenic mucocutaneous
infections, pneumonia, diminished respiratory burst,
and abnormal cell adherence in chemotaxis, causing poor
wound healing among other features.
LFA-2
A T cell antigen that is the receptor molecule for sheep
red cells, also known as the T11 antigen and leukocytefunction-associated
antigen 2 (LFA-2). The molecule has a
weight of 50 kDa. The antigen also seems to be involved in
cell adherence, probably binding LFA-3 as its ligand.
LFA-3
A 60-kDa polypeptide chain expressed on the surfaces of B
cells, T cells, monocytes, granulocytes, platelets, fibroblasts,
and endothelial cells of vessels. It is the ligand for
CD2 and is encoded by genes on chromosome 1 in humans.
LGLs (large granular lymphocyte or null cells)
These lymphocytes do not express B and T cell markers,
but have Fc receptors for immunoglobulin G (IgG) on their
surfaces. They comprise approximately 3.5% of lymphocytes
and originate in the bone marrow. LGLs include
natural killer (NK) cells (70%) and killer cells that mediate
antibody-dependent cell-mediated cytotoxicity (ADCC).
LGSP (leukocyte sialoglycoprotein)
A richly glycosylated protein present on thymocytes and T
lymphocytes. B lymphocytes are devoid of LGSP.
Liacopoulos phenomenon (nonspecific tolerance)
The daily administration of 0.5 to 1.0 g of bovine γ globulin
and bovine serum albumin to guinea pigs for at least 8 days
suppresses their immune responses to these antigens. If an
unrelated antigen is injected and continued for several days
thereafter, the response to the unrelated antigen is reduced.
This phenomenon has been demonstrated for circulating
antibody, delayed hypersensitivity, and graft-vs.-host reaction.
It describes the induction of nonspecific immunosuppression
for one antigen by the administration of relatively
large quantities of an unrelated antigen.
liberated CR1
A truncated complement receptor 1 (CR1) without transmembrane
and intracytoplasmic domains that may help
limit the size of myocardial infarcts by diminishing
complement activation. Liberated CR1 may also play a
therapeutic role in other types of ischemia, burns, autoimmunity,
and inflammation because it is a natural inhibitor of
complement activation.
lichenification
Profound hyperkeratosis or skin thickening produced by
chronic inflammation.
LICOS
The ligand for ICOS, a CD28-related protein induced on
activated T cells that can enhance T cell responses. LICOS is
formed on activated dendritic cells, B cells, and monocytes.
Li–Fraumeni syndrome
Inherited susceptibility to selected tumors, usually attributable
to germline mutations of p53.
ligand
A molecule that binds or forms a complex with another
molecule such as a cell surface receptor.
light chain
A 22-kDa polypeptide chain found in all immunoglobulin
molecules. Each four-chain immunoglobulin monomer contains
two identical light polypeptide chains joined to two
like heavy chains by disulfide bonds. The two types of light
L