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liver–kidney microsome 1 (LKM-1) autoantibodies 458 long-acting thyroid stimulator (LATS)
antibodies can be shown to interact with hepatocyte and
proximal renal tubule cell cytoplasm. The antibodies are
not demonstrable in the sera of non-A, non-B chronic
active hepatitis patients.
liver–kidney microsome 1 (LKM-1) autoantibodies
Autoantibodies associated with autoimmune hepatitis type
II. Their principal feature is the exclusive staining of the
P3 portions of the proximal renal tubules. Sixty-seven
percent of patients with this disease have antibodies to
liver cytosol type I (anti-LC-1). Cytochrome P-450 2D6
is the major antigen for LKM-1 autoantibodies, which are
specific for cytoplasmic constituents of hepatocytes and
proximal renal tubule cells. They are present in selected
patients with antinuclear antibody (ANA)-negative autoimmune
chronic active hepatitis (CAH) (HBsAg negative).
They are not found in CAH non-A, non-B. LKM-1autoantibody-positive
CAH type II is the most frequent
autoimmune liver disease in children, who have a relatively
poor prognosis. LKM-1 autoantibodies are not believed
to be pathogenic in autoimmune CAH of children. They
show specificity for cytochrome P-450. LKM-2 autoantibodies
are present in tienilic acid (Ticrynafen)-induced
hepatitis. LKM-3 autoantibodies are present in 10% of
chronic delta virus hepatitis cases. The LKM-1 antigen is
cytochrome P-450IID6. The LKM-2 antigen is cytochrome
P-450IIC8/9/10.
liver–kidney microsome 2 (LKM-2) autoantibodies
Antibodies associated only with drug-induced hepatitis
caused by tienilic acid and not an autoimmune hepatitis.
These antibodies are specific for cytochrome P-450-2 C9.
liver–kidney microsome 3 (LKM-3) autoantibodies
An autoantibody that detects a protein band of 55 kDa in
approximately 10% of patients with autoimmune chronic
hepatitis type II.
liver membrane (LM) antibodies
Antibodies specific for the 26-kDa LM protein target antigen
in the sera of 70% of autoimmune chronic active hepatitis
patients who are HBsAg-negative. These antibodies are
demonstrable by immunofluorescence, and they may also
be demonstrated in patients with primary biliary cirrhosis,
chronic hepatitis B, alcoholic liver disease, and sometimes
Sjögren’s syndrome. Lupoid autoimmune chronic active
hepatitis patients may develop antibodies against liver
membrane and also against smooth muscle and nuclear
constituents. Liver membrane antibodies are not useful for
diagnosis or prognosis.
liver membrane autoantibodies
A heterogeneous group of autoantibodies that include
liver-specific membrane lipoprotein (LSMP) autoantibodies
linked to chronic autoimmune hepatitis (AIH). They
lack disease specificity but are useful prognostically for
treatment withdrawal. Characteristic autoantibodies usually
aid in the diagnosis of autoimmune hepatitis. Persistence or
reappearance of liver-specific protein antibodies in chronic
AIH patients in remission during treatment withdrawal may
signify reactivation of the disease.
LM autoantibodies
Antimicrosomal antibodies that react exclusively with liver
tissue have been found in drug-induced hepatitis caused by
dihydralazine. They interact with cytochrome P-450-1A2.
LM antibodies against cytochrome P-450-1A2 in non-druginduced
autoimmune liver disease suggest that the liver
disease may be a manifestation of autoimmune polyendocrine
syndrome type II (APS-1).
LMP-2 and LMP-7
Catalytic subunits of the organelles (proteasomes) that
degrade cytosolic proteins into peptides in the major histocompatibility
complex (MHC) class I pathway of antigen
presentation. MHC genes encode these two subunits that
are upregulated by INF-γ and are especially significant in
the generation of MHC class I-binding peptides.
LMP genes
Two genes located in the major histocompatibility complex
(MHC) class II regions in humans and mice that code for
proteasome subunits. They are closely associated with the
two TAP genes.
L o dose (historical)
The largest amount of toxin that, when mixed with one
unit of antitoxin and injected subcutaneously into a 250-g
guinea pig, produces no toxic reaction.
local acquired resistance
Metabolic changes in plant cells that result in the deposition
or cross linking of lipoproteins and other locally acquired
resistance molecules to strengthen plant cell walls and
isolate a pathogenic microorganism. Antimicrobial peptides
and plant regulatory peptides that activate pathogenesisrelated
proteins are induced.
local anaphylaxis
A relatively common type I immediate hypersensitivity
reaction. Local anaphylaxis is mediated by immunoglobulin
E (IgE) cross linked by allergen molecules at the surfaces
of mast cells that then release histamines and other pharmacological
mediators that produce signs and symptoms.
The reaction occurs in a particular target organ such as the
gastrointestinal tract, skin, or nasal mucosa. Hay fever and
asthma represent examples.
local immunity
Immunologic reactivity confined principally to a particular
anatomic site such as the respiratory or gastrointestinal
tract. Local antibodies and lymphoid cells present in the
area may mediate a specific immunologic effect. For
example, secretory IgA produced in the gut may react to
food or other ingested antigens.
loci
Plural of locus.
locus
The precise location of a gene on a chromosome or other
marker; the DNA at that position. The use of locus is sometimes
restricted to regions of DNA that are expressed.
locus accessibility
The extent to which the chromatin architecture of a specific
antigen receptor gene permits it to be a substrate for the
recombinase complex. Controlled by enhancers.
London forces
Forces that contribute somewhat to the stabilization of
the antigen–antibody complex resulting from attraction of
oscillating dipoles of atoms and molecules moving their
electrons from one side to another. Dispersion forces occur
only when the two molecules are very close together and
decrease with the sixth power of the distance between
interaction groups.
long-acting thyroid stimulator (LATS)
An immunoglobulin G (IgG) autoantibody that mimics
the action of thyroid-stimulating hormone in its effect on