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plaque-forming cells 575 plasma cells
antibody on their surface will be lysed. Circular areas of
hemolysis appear in the gel medium. If viewed under a
microscope, a single antibody-forming cell can be identified
in the center of the lytic area. This assay has several modifications
since antibodies other than IgM may fix complement
less efficiently. In order to enhance the effects, an antiglobulin
antibody called developing antiserum is added to the
mixture. The latter technique is called indirect PFC assay.
plaque-forming cells
The antibody-producing cells in the centers of areas of hemolysis
observed microscopically during a hemolytic plaque
assay. The antibodies they form are specific for red blood
cells suspended in the gel medium surrounding them. Once
complement is added, the antibody-coated erythrocytes lyse,
producing clear areas of hemolysis surrounding the antibodyforming
cells. The antibody produced may be specific both
for red blood cell surface antigens and also for soluble antigens
deliberately coated on their surfaces for assay purposes.
plaque technique
Refer to hemolytic plaque assay and phage neutralization assay.
plasma
A transparent yellow material that constitutes 50 to 55%
of blood volume. It is 92% fluid and 7% protein. Inorganic
salts, hormones, sugars, lipids, and gases comprise the
remaining 1%. Plasma from which fibrinogen and clotting
factors have been removed is known as serum.
plasmablast
An immature cell of the plasma cell lineage that reveals distinctive,
clumped nuclear chromatin, developing endoplasmic
reticulum, and a Golgi apparatus; a B lymphocyte in a
lymph node that is beginning to reveal plasma cell features.
Manifests increased rough endoplasmic reticulum, Golgi
apparatus, and ribosomes.
plasma cell antigen
A murine plasmacyte membrane alloantigen. It may be
designated PC-1 or PC-2.
plasma cell dyscrasias
Lymphoproliferative disorders in which monoclonal plasma
cell proliferation leads to such conditions as multiple
myeloma or to the less ominous extramedullary plasmacytoma.
A diverse assemblage of neoplastic diseases characterized
by proliferation of a single cell clone producing
an M component, a monoclonal immunoglobulin, or
immunoglobulin fragment. The cells often have plasma cell
morphology but may resemble lymphocytic or lymphoplasmacytic
cells.
plasma cell leukemia
A malignancy associated with plasma cells in the circulating
blood that constitute greater than 20% of the leukocytes.
The absolute plasma cell number is more than 2000
per cubic millimeter of blood. Advanced cases reveal
extensive infiltration of the tissue with plasma cells and
replacement of the marrow. Reactive plasmacytosis must be
considered in the diagnosis.
plasma cells
Terminally differentiated antibody-producing B cells that fail
to express MHC class II or mIg and are incapable of receiving
further T cell help. Immunoglobulins are present
in their cytoplasm, and secretion of immunoglobulin by
plasma cells has been directly demonstrated in vitro. Increased
levels of immunoglobulins in some pathologic conditions
are associated with increased numbers of plasma cells and
14–20 µm.
Diagram of a plasma cell.
Plasma cell in peripheral blood.
Plasma cell in peripheral blood.
Plasma cells in peripheral blood smear.
conversely their number at antibody-producing sites increases
following immunization. Plasma cells develop from B cells
and are large, spherical, or ellipsoidal cells, 10 to 20 μm in
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