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polymeric Ig 583 polymyositis (PM)
the original DNA segment is transformed into millions
of copies. PCR methodology has been used for multiple
purposes including detection of human immunodeficiency
virus 1 (HIV-1), prenatal diagnosis of sickle cell anemia,
and gene rearrangements in lymphoproliferative disorders
among other applications. The technique is used principally
to prepare enough DNA for analysis by available
methods and is used widely in diagnostic work. PCR has a
99.99% sensitivity.
polymeric Ig
Immunoglobulin molecules comprised of numerous identical
H 2L 2 monomers linked by a J chain. Pentameric IgM
[(H 2L 2)5], with ten antigen-binding sites and dimeric IgA
[(H 2L 2)2] with four, are examples.
polymers
Molecules composed of more than one repeating unit;
immunoglobulins composed of more than one basic
monomeric four-polypeptide chain unit. IgAs may exist as
dimers with two units or as multimers. The IgM molecule is
pentameric, containing five monomeric units.
polymorphism
The occurrence of different variants of a gene or trait in
a population. The presence of two or more forms such as
ABO and Rh blood groups, in individuals of the same
species. This is due to two or more variants at a certain
genetic locus occurring with considerable frequency in a
population. Polymorphisms are also expressed in the human
leukocyte antigen (HLA) system, as well as in allotypes of
immunoglobulin γ and κ chains. Genetic polymorphism
refers to the presence of two or more alleles of a given gene
within a population with the variant alleles each appearing
at a frequency >1%.
9–15 µm
Schematic representation of a polymorphonuclear leukocyte (PMN).
polymorphonuclear leukocyte (PMN)
White blood cells with lobulated nuclei that are often
trilobed. PMNs are of myeloid cell lineage and in mature
form may be differentiated into neutrophils, eosinophils,
and basophils. This distinction is based on the staining
characteristics of their cytoplasmic specific or secondary
granules. PMNs measure approximately 13 μm in diameter
and are active in acute inflammatory responses.
polymyositis (PM)
An acute or chronic inflammatory disease of muscle,
involving fibers of the voluntary muscles; it is twice as
common in women as in men. Lymphocytes in polymyositis
Substances Associated with Neutrophils
Azurophil Granules
(Primary Granules)
Specific Granules
(Secondary Granules)
Bacterial permeabilityinducing
protein (BPI)
Cathepsin G
Cationic antimicrobial
protein (CAP) 57
Cationic antimicrobial
protein (CAP) 37
Defensins:
HP1
HP2
HP3
Elastase
Lysozyme
Myeloperoxidase Bacterial chemotaxin receptors
Collagenase
C5a receptors
Gelatinase
Lactoferrin
Lysozyme
NADPH
Vitamin B 12-binding protein
Polymorphonuclear leukocyte (PMN).
subjects produce a cytotoxin when incubated with autologous
muscle. Biopsies of involved muscle reveal infiltration
by lymphocytes and plasma cells. PM characteristically
manifests autoantibodies against aminoacyl tRNA
synthetases. Antibodies can be demonstrated against the
nuclear antigens Jo-1, PM-Scl, and RNP. Patients may
develop polyclonal hypergammaglobulinemia. One fifth of
patients may develop rheumatoid factors and antinuclear
antibodies. Cellular immunity appears important in the
pathogenesis, as exemplified by lymphocytes of patients
with polymyositis responding to their own muscle antigens
as if they were alien. Patients often complain of muscle
weakness, especially in the proximal muscles of extremities.
To diagnose polymyositis, a minimum of three of the
following must be present: (1) shoulder or pelvic girdle
weakness, (2) myositis as revealed by biopsy, (3) increased
P