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insulin receptor autoantibodies 394 integrins, HGF/SF activation of
Insulin-like growth factors (IGFs)
insulin-dependent and non-insulin-dependent diabetes mellitus
may have insulin receptor antibodies that react at either
the site that binds insulin or at some other binding region.
insulin receptor autoantibodies
Autoantibodies that induce type B insulin resistance. This
syndrome may be accompanied by acanthosis nigricans
and autoimmune disease. Selected patients with insulindependent
diabetes mellitus (IDDM) and non-insulindependent
diabetes mellitus have antibodies that react with
these insulin receptors at their insulin-binding site or other
binding sites. Individuals who have insulin autoantibodies
and islet cell antibodies and first-degree relatives of patients
with IDDM have a predictive value of 60 to 77% for the
development of IDDM within 5 to 10 years.
insulin resistance
Diminished responsiveness to insulin as revealed by its
decreased capacity to induce hypoglycemia may or may not
have an immunologic basis. The administration of bovine
or porcine insulin to humans can lead to antibody production
that may contribute to insulin resistance.
insulitis
Lymphocytic or other leukocytic infiltration of the islets
of Langerhans in the pancreas, which may accompany the
development of diabetes mellitus.
Intal ®
Commercial preparation of disodium cromoglycate.
integrase
Retroviral enzyme such as the HIV enzyme that facilitates
insertion of viral DNA into the genome of the host cell.
integrin family of leukocyte adhesive proteins
The CD11/CD18 family of molecules.
integrins
A family of cell membrane glycoproteins that are heterodimers
comprised of α and β chain subunits and serve as
extracellular matrix glycoprotein receptors. They identify
the RGD sequence of the β subunit, which consists of the
arginine–glycine–aspartic acid tripeptide that occasionally
also includes serine. The RGD sequence serves as a receptor
recognition signal. Extracellular matrix glycoproteins,
for which integrins serve as receptors, include fibronectin,
C3, and lymphocyte-function-associated antigen 1 (LFA-1),
among other proteins. Differences in the β chain serve as
the basis for division of integrins into three categories. Each
category has distinctive α chains. The β chain provides
specificity. The same 95-kDa β chain is found in one
category of integrins that includes LFA-1, p150, p95, and
complement receptor 3 (CR3). The same 130-kDa β chain
is shared among VLA-1, VLA-2, VLA-3, VLA-4, VLA-5,
VLA-6, and integrins found in chickens. A 110-kDa β chain
is shared in common by another category that includes
the vitronectin receptor and platelet glycoprotein IIb/IIIa.
There are four repeats of 40-amino acid residues in the
β chain extracellular domains, and there are 45-amino acid
residues in the β chain intracellular domains. The principal
function of integrins is to link the cytoskeleton to extracellular
ligands. They also participate in wound healing,
cell migration, killing of target cells, and phagocytosis.
Leukocyte adhesion deficiency syndrome occurs when the
β subunit of LFA-1 and Mac-1 are missing. VLA proteins
facilitate binding of cells to collagen (VLA-1, -2, and -3),
laminin (VLA-1, -2, and -6), and fibronectin (VLA-3, -4,
and -5). The cell-to-cell contacts formed by integrins are
critical for many aspects of the immune response such as
antigen presentation, leukocyte-mediated cytotoxicity, and
myeloid cell phagocytosis. Integrins comprise an essential
part of an adhesion receptor cascade that guides leukocytes
from the bloodstream across endothelium and into injured
tissues in response to chemotactic signals.
integrins, HGF/SF activation of
Integrins and growth factor receptors can share common
signaling pathways. Each type of receptor can impact the
signal and ultimate response of the other. An example of a
growth factor shown to influence members of the integrin
family of cell adhesion receptors is hepatocyte growth
factor/scatter factor (HGF/SF), a multifunctional cytokine
that promotes mitogenesis, migration, invasion, and
morphogenesis. HGF/SF-dependent signaling can modulate
integrin function by promoting aggregation and cell
adhesion. Morphogenic responses to HGF/SF are dependent
on adhesive events. HGF/SF-induced effects occur via
signaling of the MET tyrosine kinase receptor, following
ligand binding. HGF/SF binding to MET leads to enhanced
integrin-mediated B cell and lymphoma cell adhesion.
Blocking experiments with monoclonal antibodies directed
against integrin subunits indicate that α 4β1 and α 5β1 integrins
on hematopoietic progenitor cells are activated by HGF/SF
to induce adhesion to fibronectin. The HGF/SF-dependent
signal transduction pathway can also induce ligand binding
activity in functionally inactive α vβ3 integrins. The effects
of HGF/SF highlight the importance of growth factor regulation
of integrin function in both normal and tumor cells.