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purine nucleoside phosphorylase (PNP) 603 pyrogen
Pulmonary vasculitis. Note necrosis of endothelial cells and supporting
stromal structures with acute and chronic inflammation and
exudation of polymorphonuclear leukocytes (PMNs), eosinophils,
and extravasated erythrocytes (50× magnification).
Pulmonary vasculitis. Direct immunofluorescence reveals coalescent and
granular deposits of IgM and C3 in the walls of some muscular arteries
and occasional large veins consistent with immune complex vasculitis
involving large vessels (200× magnification).
Pulmonary vasculitis. Direct immunofluorescence reveals coalescent and
granular deposits of IgM and C3 in the walls of some muscular arteries
and occasional large veins consistent with immune complex vasculitis
involving large vessels (500× magnification).
purine nucleoside phosphorylase (PNP)
An enzyme involved in purine metabolism. A deficiency of
this enzyme leads to the accumulation of purine nucleosides
that are toxic for developing T lymphocytes and severe
combined immunodeficiency.
purine nucleoside phosphorylase (PNP) deficiency
A type of severe combined immunodeficiency caused by
mutant types of PNP that results in the retention of metabolites
that have toxic effects on T cells. B lymphocytes appear
unaffected and their numbers are normal. All cells of mammals
contain PNP, which acts as a catalyst in the phosphorolysis
of guanosine, deoxyguanosine, and inosine. Insufficient
PNP leads to an elevation in the concentration within cells
of deoxyguanosine, guanosine, deoxyguanosine triphosphate
(dGTP), and guanosine triphosphate (GTP). dGTP
blocks the ribonucleoside-diphosphate reductase enzyme
that participates in DNA synthesis. T cell precursors are
especially sensitive to death induced by these compounds.
PNP is composed of three 32-kDa subunits. Its gene, located
on chromosome 14q13.1, codes for a 289-amino acid residue
polypeptide chain. Immunologic defects associated with this
disorder are characterized by anergy, lymphocytopenia,
and diminished T lymphocytes. By contrast, serum immunoglobulin
levels and the response following deliberate
immunization with various types of immunogens are within
normal limits. Inheritance is autosomal-recessive. Treatment
is by bone marrow transplantation.
purpura
Purple areas on the skin caused by bleeding into the skin.
purpura hyperglobulinemia
Hemorrhagic areas around the ankles or legs in patients
whose serum immunoglobulin levels are strikingly
increased. Examples include Waldenström’s macroglobulinemia,
multiple myeloma, and Sjögren’s syndrome.
pyogenic bacteria
Microorganisms, such as Gram-positive staphylococci and
streptococci, that induce predominantly polymorphonuclear
leukocyte (PMN) inflammatory responses, leading to the
formation of pus at sites of infection.
pyogenic infection
An infection associated with the generation of pus.
Microorganisms that are well known for their pus-inducing
or pyogenic potential include Streptococcal pyogenes,
Staphylococcus aureus, Streptococcus pneumoniae, and
Hemophilus influenzae. Antibody-deficient patients and
those having defective phagocytic cell capacity show
increased susceptibility to pyogenic infections. Patients with
complement deficiency such as C3 deficiency, factor I deficiency,
etc. are also prone to develop pyogenic infections.
pyogenic microorganisms
Microorganisms that stimulate a large polymorphonuclear
leukocyte response to their presence in tissues.
pyrogen
A substance that induces fever. The fever may be either endogenously
produced, such as by interleukin-1 (IL1) released from
macrophages and monocytes, or an endotoxin associated with
Gram-negative bacteria produced exogenously.
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