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pFc′ fragment 568 phagocyte
Platelets and megakaryocytes represent the tissue source.
Fibroblasts, platelets, adrenal microvascular pericytes, mast
cells, basophils, and megakaryocytes are the target cells. PF4
levels increase during cardiopulmonary bypass surgery, in arterial
thrombosis, following surgery, in acute myocardial infarction,
during acute infections, and during inflammation.
pFc′ fragment
A fragment of pepsin digestion of immunoglobulin G (IgG)
or the Fc fragment that yields low molecular weight peptides
and a pFc′ fragment that is still capable of binding to
an Fc receptor on a macrophage or monocyte. It is a 27-kDa
dimer without a covalent bond composed of two C H3
domains, the carboxyl terminal 116-amino acid residues
of each chain. Unlike the Fc′ fragment, it has the basic N
terminal and C terminal peptides of this immunoglobulin
domain.
PFC (plaque-forming cell)
An in vitro technique in which antibody-synthesizing cells
derived from the spleen of an animal immunized with a
specific antigen produce antibodies that lyse red blood cells
coated with the corresponding antigen in the presence of
complement in a gel medium. The reaction bears some
resemblance to β hemolysis produced by streptococci on a
blood agar plate. When examined microscopically, a single
antibody-producing cell can be detected in the center of the
plaque-forming unit.
Richard Pfeiffer.
Pfeiffer, Richard (1858–1945)
Pfeiffer was a colleague of Robert Koch in Berlin. He observed
that Vibrio cholerae organisms were lysed in the peritoneum
of immunized guinea pigs and showed the same process in
vitro. This became known as Pfeiffer’s phenomenon.
Pfeiffer’s phenomenon
The rapid lysis of Vibrio cholerae microorganisms injected
into the peritoneal cavities of guinea pigs immunized
against them. The microorganisms are first rendered nonmotile,
followed by complement-induced lysis in the presence
of antibody. Immune bacteriolysis in vivo involving
Vibrio cholera became known as Pfeiffer’s phenomenon.
PFU
Abbreviation for plaque-forming unit. An assay of plaques that
develop in hemolytic plaque assays and related techniques.
PHA
Abbreviation for phytohemagglutinin. PHA is principally
a T lymphocyte mitogen, producing a greater stimulatory
effect on CD4 + helper/inducer T lymphocytes than on CD8
suppressor/cytotoxic T cells. It has a weaker mitogenic
effect on B lymphocytes.
phacoanaphylactic endophthalmitis
Introduction of lens protein into the circulation following
an acute injury of the eye involving the lens may result in
chronic inflammation of the lens as a consequence of autoimmunity
to lens protein.
phacoanaphylaxis
Hypersensitivity to lens protein of the eye following an
injury that introduces lens protein, normally a sequestered
antigen, into the circulation. The immune system does not
recognize it as self and responds to it as it would any other
foreign antigen.
phage display
A technique that permits expression of the humoral immune
system in vitro by phage display technology and antibody
engineering. Large libraries of antibody fragments are
displayed on the surfaces of bacteriophage particles. Phages
expressing desirable antibody specificity must be selected
and expanded. Favorable mutations in the genes encoding
a selected antibody specificity must be selected. Antibody
fragments are selected from large libraries constructed from
B cells or assembled in vitro from the genetic elements
encoding antibodies. This technique is rapid and unaffected
by the immunogenicity of the target antigen. Selection
procedures permit the isolation of antibodies specific for
membrane molecules and epitopes. Antibody fragments
can be tailored to have the desired avidity, pharmacokinetic
properties, and biological effector functions. Monoclonal
antibodies prepared from phage display libraries formed
from human V regions constitute a molecule especially
amenable for immunotherapy in humans.
phage antibody library
Cloned antibody variable region gene sequences that may
be expressed as Fab or svFv fusion proteins with bacteriophage
coat proteins. They can be exhibited on phage
surfaces. The phage particle contains the gene encoding a
monoclonal recombinant antibody and can be selected from
the library by binding of the phage to specific antigen.
phage display library
Antibody-like phage produced by cloning immunoglobulin
V region genes and filamentous phage which results in
their expressing antigen-binding domains on their surfaces.
Antigen-binding phage can be replicated in bacteria and
used like antibodies. This method can be employed to
develop antibodies of any specificity.
phage neutralization assay
A laboratory test in which bacteriophage is combined
with antibodies specific for it to diminish its capacity to
infect a host bacterium. This neutralization of infectivity
may be quantified by showing the decreased numbers of
plaques produced when the phage that has been incubated
with specific antibody is plated on appropriate bacteria.
The technique is sensitive and can demonstrate even weak
antibody activity.
phagocyte
A cell capable of phagocytosis, for example, mononuclear
phagocytes and polymorphonuclear neutrophils that ingest