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Percoll® 565 peripheral lymphoid organs
Percoll®
A density-gradient centrifugation medium used to isolate
certain cell populations such as natural killer (NK) cells. It
is a colloidal suspension.
perforin
Perforin from cytolytic T lymphocyte and natural killer
(NK) cell granules produces target cell lysis. Perforin isolation
and sequence determination through cDNA cloning
made possible studies on perforin structure and function.
Perforin is a 70-kDa glycoprotein. Granules containing
perforin mediate lysis in a medium with calcium. A
transmembrane polyperforin tubular channel is formed in
the lipid bilayer of the membrane. Released perforin inserts
into the membranes of target cells to produce 5- to 20-nm,
doughnut-shaped, polymeric structures that serve as stable
conduits for intracellular ions to escape to the outside extracellular
environment, promoting cell death. Both murine and
human perforin cDNAs have been cloned and sequenced.
They share 67% homology, and each is 534 amino acids
long. Perforin and C9 molecules appear to be related in a
number of aspects. This is confirmed by sequence comparison,
functional studies, and morphologic and immunologic
comparisons. Whereas lysis of host cells by complement is
carefully regulated, cytotoxic T lymphocytes lyse virusinfected
host cells. Decay-accelerating factor (DAF) and
homologous restriction factor (HRF) guard host cells against
lysis by complement. By contrast, perforin is able to mediate
lysis without such control factors. Using perforin cDNA as
the hybridization probe, mRNA levels have been assayed for
perforin expression. Thus far, all cytotoxic T lymphocytes
have been shown to express the perforin message. Perforin
expression is an in vitro phenomenon, but perforin expression
has been shown in vivo. This was based upon cytotoxic
CD8 + T cells containing perforin mRNA. Refer also to
perforin–granzyme-mediated cytotoxicity.
perforin–granzyme-mediated cytotoxicity
A means whereby proteases (granzymes) and a poreforming
protein (perforin) fatally injure target cells when
these enzymes are released by degranulation from cytotoxic
T lymphocytes, NK cells, or NKT cells. Following the
uptake of these molecules by the target cells, perforin aids
the release of granzyme from endosomes of target cells.
Presynthesized perforin and granzyme are held in the cytoplasmic
granules of the cells.
periarteriolar lymphoid sheath (PALS)
The thymus-dependent region in the splenic white pulp
populated mainly by T cells. Lymphocyte cuffing of these
small arterioles of the spleen adjacent to lymphoid follicles
is observed. Two thirds of the PALS T cells are CD4 + and
one third are CD8 + . During humoral immune responses
against protein antigens, B cells are activated at the PALS
and follicle interfaces and then migrate into the follicles
to produce germinal centers. In addition to mature T cells
and some B cells, PALS also contain plasma cells, macrophages,
and interdigitating dendritic cells.
periarteritis nodosa
A synonym for polyarteritis nodosa.
perinuclear antibodies
Antibodies against perinuclear granules in buccal mucosal
cells in humans. They are present in about 78% of patients
with classical rheumatoid arthritis (RA) and in 40% of
patients with RA who are IgM rheumatoid factor (RF)-
negative. The presence of perinuclear antibodies portends
a poor prognosis in the RF-negative group. Perinuclear
antibodies may also be found in selected other rheumatic
diseases and are often present in subjects infected with
Epstein–Barr virus. They are also demonstrable in approximately
one fourth of patients with primary biliary cirrhosis.
perinuclear factor (profillagrin) autoantibodies
Autoantibodies against perinuclear granules of human buccal
mucosal cells, They are positive in 78% of patients with
classical rheumatoid arthritis (RA) and in 40% of patients
with RA who are IgM rheumatoid factor (RF)-negative.
The presence of these antibodies in RF-negative individuals
signals a poor prognosis. They are present in much higher
titers in RA patients than in individuals with other rheumatic
diseases. The principal target antigen is profillagrin,
an insoluble protein rich in histidine.
peripheral blood mononuclear cells
Lymphocytes and monocytes in the peripheral blood that
may be isolated by Ficoll-Hypaque density centrifugation.
peripheral lymphoid organs
Lymphoid organs that are not required for ontogeny of the
immune response. They include the lymph nodes, spleen,
tonsils, and mucosal-associated lymphoid tissues in which
immune responses are induced, in contrast to the thymus, a
central lymphoid organ in which lymphocytes develop.
Tonsil
Lymph nodes
Peyer’s
patches in
GALT
Peripheral lymphoid organs.
Spleen
Lymph nodes
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