Untitled - D Ank Unlimited

factor H deficiency 263 Faenia rectivirgula
with C3b and facilitates dissociation of alternative complement
pathway C3 convertase, designated C3bBb, into C3b
and Bb. Factor I splits C3b if factor H is present. In humans,
factor H is a 1231-amino-acid residue, single polypeptide
chain. It is comprised of 20 short homologous repeats composed
of about 60 residues present in proteins that interact
with C3 or C4. Factor H is an inhibitor of the alternative
complement pathway. Previously called β-1H globulin.
factor H deficiency
Extremely rare genetic deficiency of factor H that has an
autosomal-recessive mode of inheritance. Only 1% of
the physiologic level of factor H is present in the sera of
affected individuals, which renders them susceptible to
recurrent infections by pyogenic microorganisms. People
who are heterozygotes have 50% of normal levels of factor
H in their sera and show no clinical effects.
factor H receptor (fH-R)
A receptor that initial studies have shown to be comprised
of a 170-kD protein expressed by Raji cells and tonsil
B cells. Neutrophils, B lymphocytes, and monocytes
express fH-R activity.
factor I
A serine protease that splits the α chain of C3b to produce
C3bi and the α chain of C4b to yield C4bi. Factor I splits
a 17-amino-acid residue peptide termed C3f, if factor H or
complement receptor 1 are present, from the C3b α chain to
yield C3bi. Factor I splits the C3bi, if complement receptor
I or factor H are present, to yield C3c and C3dg. Factor I
splits the C4b α chain, if C4-binding protein is present, to
yield C4bi. C4c and C4d are produced by a second splitting
of the α chain of C4bi. Factor I is a heterodimeric molecule.
It is also called C3b/C4b inactivator.
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Papain
digestion
Generation of Fabc fragment by papain digestion of IgG in which one Fab region is cleaved, leaving an Fabc fragment consisting of the Fc region and one
Fab region of the molecule bearing a single antigen-binding site.
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Plasmin
digestion
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Fab
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Fabc
factor I deficiency
Very uncommon genetic deficiency of C3b inactivator that
has an autosomal-recessive pattern of inheritance. Less
than 1% of the physiologic level of factor I is present in the
sera of affected subjects, which renders them susceptible
to repeated infections by pyogenic microorganisms. These
individuals also reveal deficiencies of factor B and C3 in
their serum, as these components are normally split in
vivo by alternative pathway C3 convertase (C3bBb), which
factors I and H inhibit under physiologic conditions. These
patients may develop urticaria because of the formation of
C3a, which induces the release of histamine.
factor P (properdin)
A key participant in the alternative pathway of complement
activation. It is a globulin, but not an immunoglobulin, that
combines with C3b and stabilizes alternative pathway C3
convertase (C3bB) to produce C3bBbP. Factor P is a 3- or
4-polypeptide chain structure.
factor VIII
A coagulation protein produced by endothelial cells, which
makes it a useful marker for vascular tumors. It is demonstrable
by immunoperoxidase staining. Megakaryocytes
and platelets also stain for factor VIII.
facultative phagocytes
Cells such as fibroblasts that may show phagocytic properties
under special circumstances.
FAE
Refer to follicle-associated epithelium.
Faenia rectivirgula
The most frequently encountered inhalant in farmer’s
lung disease, the most common type of hypersensitivity
pneumonitis in the United States. This agent or its
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Facb
Generation of Facb fragment through plasmin digestion of an IgG molecule.
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F