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phosphatase 572 phytohemagglutinin (PHA)
c-abl
9
H 3 C
O
22
bcr
Philadelpia chromosome.
Phorbol 12,13-dibutyrate
(PDBu)
H 3C
HO
H
bcr/abl fusion gene
synthesis and cell proliferation, induction of prostaglandin
formation, alteration in the morphology and
permeability of cells, and disappearance of surface
fibronectin. PMA also acts on leukocytes. It links to and
stimulates protein kinase C. This leads to threonine and
serine residue phosphorylation in the transmembrane
protein cytoplasmic domains such as in the CD2 and
CD3 molecules. These events enhance interleukin-2
(IL2) receptor expression on T cells and facilitate their
proliferation in the presence of IL1 as well as TPA. Mast
cells, polymorphonuclear leukocytes, and platelets may
all degranulate in the presence of TPA.
phosphatase
An enzyme that deletes phosphate groups from protein
amino acid residue side chains. Lymphocyte protein phosphatases
control signal transduction and transcription factor
activity. Protein phosphatases may show specificity for
phosphotyrosine residues or phosphoserine and phosphothreonine
residues.
phosphatidylinositol bisphosphate (PIP 2)
A membrane-associated phospholipid cleaved by a phospholipase
C-γ to yield the signaling molecules discylglycerol
and inositol triphosphate.
phosphocholine antibodies
Antibodies synthesized during some bacterial infections
especially by streptococcus (S) but also by Mycoplasma,
Proteus, Trichinella, and Neisseria in addition to
helminthic parasites. CD5 + B cells form IgM antibodies that
have a limited idiotype spectrum and V H/V L gene usage and
provide protective immunity from infection. These antibodies
cross-react with phosphotidylcholine, pneumococci,
dsDNA, and sphingomyelin. Phosphocholine antibody
affinity diminishes with age.
O
CH 3(CH 2) 2CO
H
OC(CH2) 2CH3 CH3 H
O
H
CH 2 OH
Structure of phorbol ester.
CH 3
phospholipase C-
A principal enzyme in signal transduction. It is activated
by protein tyrosine kinases that are activated by receptor
ligation. Activated phospholipase C-γ cleaves inositol phospholipid
into inositol triphosphate (IP 3) and diacylglycerol
(DAG).
phospholipase C (PLC-)
An enzyme that participates in signal transduction involved
in T and B cell activation. It cleaves phosphatidylinositol
bisphosphate (PIP 2) into diacylglycerol (DAG) and inositol
triphosphate (IP 3), initiating activation of two principal
signaling pathways.
phospholipid autoantibodies
Autoantibodies that include those specific for cardiolipin,
phosphatidylserine, and lupus present in individuals with
antiphospholipid antibody syndrome and systemic lupus
erythematosus, drug-induced disorders, and infectious and
neurological diseases. Phospholipid autoantibodies, primary
markers for antiphospholipid antibody syndrome, are linked
to increased risk of thrombosis, thrombocytopenia, and
recurrent abortion.
photoallergy
An anaphylactoid reaction induced by exposing an individual
to light.
photoimmunology
The investigation of the effects of photons on the immune
system. The effects are initiated in the skin from the
interaction of ultraviolet radiation with immune cells.
Ultraviolet-induced immune suppression may play a role in
human skin cancer induction.
phycoerythrin
An extensively used label for immunofluorescence; this
light-gathering plant protein absorbs light efficiently and
emits a brilliant red fluorescence.
phylogenetic-associated residues
Amino acid residues in immunoglobulin variable regions
at a specific position in immunoglobulin (or other protein)
molecules in one or more species.
phylogeny
The evolutionary development of a species.
phytoalexins
Plant substances that are active in phytoimmunity.
phytohemagglutinin (PHA)
A lectin or carbohydrate-binding protein, synthesized by
plants. It cross links human T lymphocyte surface molecules,
such as T cell receptors, thereby causing polyclonal
activation and T cell aggregation or agglutination. PHA is
used often in T lymphocyte functional studies to investigate
T cell activation. Clinically, it is employed to determine
whether a patient’s T lymphocytes are functional, or it
may be used to induce T lymphocyte mitosis to gather
karyotypic data. PHA is derived from an extract of the red
kidney bean (Phaseolus vulgaris) that contains powerful
cell-agglutinating and mitogenic principles. PHA was the
first polyclonal mitogen to be described. It allows lymphocytes
to be activated in in vitro cultures and the investigation
of lymphocyte growth and lymphokine synthesis. PHA
consists of five tetrameric glycoproteins, each of which
contains two different subunits designated ENL and have
molecular weights of 33 and 31.6 kDa, respectively. PHA
stimulates the proliferation of peripheral blood mononuclear
cells, notably T cells in the presence of monocytes