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PCP 561 pemphigus foliaceus
PCP
Abbreviation for Pneumocystis carinii pneumonia.
PCR
Abbreviation for polymerase chain reaction.
PDGF
Abbreviation for platelet-derived growth factor.
PECAM (CD31)
An immunoglobulin-like molecule present on leukocytes
and at endothelial cell junctions. The molecules participate
in leukocyte–endothelial cell interactions, as during an
inflammatory response. See also platelet endothelial cell
adhesion molecule-1 (PECAM-1; CD31).
pediatric AIDS
Acquired immunodeficiency syndrome (AIDS) in infants
who are infected vertically (i.e., from mother to young
through intrauterine or intrapartum infection). These
infants show symptoms usually between 3 weeks and
2 years of age. They develop lymphadenopathy, fever,
increased numbers of B lymphocytes in the peripheral
blood, thrombocytopenia, and increased levels of IgG,
IgM, and IgD in the serum. They may develop lymphoid
interstitial pneumonia, chronic otitis media encephalopathy,
recurrent bacterial infections, and Candida esophagitis.
Epstein–Barr virus infection may produce interstitial
pneumonia and salivary gland inflammation. The infants
may also have blood-borne infections with such microorganisms
as Hemophilus influenzae or pneumococci. The
adult age patterns of opportunistic infections and Kaposi’s
sarcoma are rarely seen in HIV-1-infected infants. These
children have a 50% 5-year mortality.
PEG (polyethylene glycol)
(1) A synthetic, inert molecule with a long chain structure
that masks recognition of certain proteins by the immune
system when attached to them. For example, PEG has been
linked to adenosine deaminase (ADA), the absence of which
may induce severe combined immunodeficiency. This PEG
attachment permits extended survival of ADA in the body.
(2) PEG is also used to promote cell fusion in hybridoma
technology, in which an antibody-secreting cell and a mutant
myeloma cell are fused to yield a hybridoma that is immortal
and continues to produce a monoclonal antibody product.
pegademase bovine
A modified enzyme used for enzyme replacement treatment of
severe combined immunodeficiency disease (SCID) associated
with adenosine deaminase deficiency. It is a conjugate
of multiple strands of monomethoxy polyethylene glycol
(PEG) covalently linked to the adenosine deaminase (ADA)
enzyme. It replaces the deficient enzyme, which when absent
leads to the accumulation of metabolites toxic to lymphocytes.
This treatment corrects metabolic abnormalities, leading to
improvement in immune function and decreased frequency
of opportunistic infections. The lag time between correction
of the metabolic abnormality and improved immune
function may vary from a few weeks to as long as 6 months.
SCID associated with ADA deficiency is rare, inherited, and
frequently fatal. Without ADA, purine substrates adenosine
and 2′-deoxyadenosine concentrations increase, leading to
metabolic abnormalities that are toxic to lymphocytes. Bone
marrow transplantation can cure the immune deficiency.
peginterferon -2a
Interferons bind to specific receptors on cell surfaces,
leading to intracellular signaling via a complex cascade of
protein–protein interactions, leading to rapid activation of
gene transcription. Genes stimulated by interferon modulate
many biological effects, including the inhibition of viral
replication in infected cells, inhibition of cell proliferation,
and immunomodulation. Peginterferon α-2a stimulates
prodution of effector proteins such as serum neopterin and
2′,5′-oligoadenylate synthetase.
Pemphigoid (primate esophagus).
pemphigoid
A blistering disease of the skin in which bullae form at
the dermal–epidermal junction, in contrast to the intraepidermal
bullae of pemphigus vulgaris. Autoantibodies
develop against the dermal basement membrane. By using
fluorochrome-labeled goat or rabbit antihuman IgG, linear
fluorescence can be demonstrated at the bases of subepidermal
bullae by immunofluorescence microscopy. Dermal
basement membrane IgG autoantibodies can also be demonstrated
in serum. This disease occurs principally in elderly
individuals. C3 linear fluorescence at the dermal–epidermal
junction is often demonstrable as well.
pemphigus erythematosus (Senear–Usher syndrome)
A clinical condition with immunopathologic characteristics
of both pemphigus and lupus erythematosus. Skin lesions
may appear on the seborrheic regions of the head and upper
trunk, as seen in pemphigus foliaceus; however, immune
deposits are also demonstrable at the dermal–epidermal
junction and in skin biopsy specimens obtained from areas
exposed to sunlight, reminiscent of lupus erythematosus.
Light microscopic examination may reveal an intraepidermal
bulla of the type seen in pemphigus foliaceus. Facial
skin lesions may even include the “butterfly rash” seen in
lupus. Immunofluorescence staining may reveal intercellular
IgG and C3 in a “chickenwire” pattern in the epidermis
with concomitant granular immune deposits containing
immunoglobulins and complement at the dermal–epidermal
junction. The serum may reveal both antinuclear antibodies
and pemphigus antibodies. Pemphigus erythematosus has
been reported in patients with neoplasms of internal organs
and in drug addicts, among other conditions. Indirect
immunofluorescence using serum with both antibodies may
reveal simultaneous staining for intercellular antibodies and
peripheral (rim) nuclear fluorescence in the same specimen
of monkey esophagus used as a substrate.
pemphigus foliaceus
A type of pemphigus characterized by subcorneal blisters
and anti-dsg1 autoantibodies. Patients develop fragile blisters
that rupture early, leaving areas of denuded skin. One
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