Untitled - D Ank Unlimited

secretor 641 secretory immunoglobulin A (SIgA)
secretor
An individual who secretes ABH blood group substances
into body fluids such as saliva, gastric juice, tears, ovarian
cyst fluid, etc. Secretors constitute at least 80% of the
human population. The property is genetically determined
and requires that a secretor be homozygous (Se/Se) or
heterozygous (Se/se) for the Se gene.
Plasma cell
J chain
Secretory component
Dimeric IgA
Mucosal
Epithelial cell
Secretory component.
Proteolytic
cleavage
site
secretory antibody
A secreted antibody that possesses a tail piece, J chain,
and secretory component subjected to post-translational
modifications that allow access to body secretions including
tears and mucus.
secretory component (SC)
A 75-kDa molecule synthesized by epithelial cells in the
lamina propria of the gut that becomes associated with
immunoglobulin A (IgA) molecules produced by plasma
cells in the lamina propria of the gut as they move across
the epithelial cell layer to reach the mucosal surface of
intestine to provide local immunity. SCs appear in three
molecular forms: as an SIgM and SIgA stabilizing chain, as
a transmembrane receptor protein, and as a free secretory
component in fluids. SC is a fragment of the poly-Ig receptor
that remains bound to Ig following transcytosis across
the epithelium and cleavage.
secretory component deficiency
A lack of immunoglobulin A (IgA) in secretions as a consequence
of the inability of gastrointestinal tract epithelial cells to
produce secretory component to be linked to the IgA molecules
synthesized in the lamina propria of the gut. Secretory component
normally prevents IgA destruction by proteolytic enzymes
in the gut lumen. The disorder is rare and is characterized by
protracted diarrhea associated with gut infection.
Secretory IgA.
Secretory
IgA
Secretory component
J chain
secretory IgA
A dimeric molecule composed of two immunoglobulin
A (IgA) monomers joined by a J polypeptide chain and
a glycopeptide secretory component that serves as the
principal molecule of mucosal immunity. IgA is the only
immunoglobulin isotype that can be selectively passed
across mucosal walls to reach the lumens of organs lined
with mucosal cells. Specific FcαRs that bind IgA molecular
dimers are found on intestinal epithelial cells. The
FcαR joins the antibody molecule to the basal surface of
the epithelial cell exposed to the blood. It is bound to the
polyimmunoglobulin receptor on the basolateral surfaces
of epithelial cells and facilitates vesicular transport of the
anchored IgA across cells to the surface of the mucosa.
Once this complex reaches its destination, FcαR (S
protein) is split in a manner that permits the dimeric IgA
molecule to retain an attached secretory piece that has a
strong affinity for mucus, thereby facilitating the maintenance
of IgA molecules on mucosal surfaces. The secretory
piece also has the important function of protecting
the secreted IgA molecules from proteolytic digestion by
enzymes of the gut, in addition to its active role in transporting
IgA molecules through epithelial cells. Secretory
or exocrine IgA appears in the colostrum, intestinal and
respiratory secretions, saliva, tears, and other secretions.
secretory immune system
A major component of the immune system that provides protection
from invading microorganisms at local sites. Much of
the effect is mediated by secretory IgA molecules in the secretions
at the mucosal surface. Immunoglobulins may also be in
clotted fluids where they protect against microorganisms.
secretory immunoglobulin A (SIgA)
SIgA may interfere with the attachment of bacteria to host cells
by coating the microbes. It may also neutralize their exotoxins,
inhibit their motility, and agglutinate them. It is not involved
in opsonization or lysis of bacteria through complement. Its
ability to prevent adherence of such microorganisms as Vibrio
cholerae, Giardia lamblia, and selected respiratory viruses to
mucosal surfaces represents a significant defense mechanism.
Although gastric acidity can destroy most microorganisms, it
does not destroy Mycobacterium tuberculosis and enteroviruses.
Gram-negative bacteria may colonize the stomach and
small intestine in subjects with achlorhydria. Unconjugated
9.
10.
11.
Respiratory
tract
Genitourinary
tract
8.
Lactating
breast
Lacrimal
glands
7.
1.
Salivary
glands
6.
Ag
Digestive
tract
2.
Blood
stream
Secretory immune system.
Intestine
5.
3.
4.
Peyer’s
patch
Plasma
cells
Mesenteric
lymph node
via lymphatic
drainage
S