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papain hydrolysis 553 paracrine factor
cpm
CONTROL
Filter
paper
disc
75% = Amount labeled
IgE added to test
Labeled IgE (IgE standard)
Labeled IgE
no antigen-binding capacity, although it does have complement-fixing
functions and attaches immunoglobulin molecules
to Fc receptors on cell membranes. The enzyme has
also been used to render red blood cell surfaces susceptible
to agglutination by incomplete antibody.
papain hydrolysis
Cleavage of immunoglobulin G (IgG) molecules into two
Fab fragments and one Fc fragment. When the immunoglobulin
is exposed to papain with cysteine present,
papain cleaves a histidyl–threonine peptide bond of the
heavy chain.
paper radioimmunosorbent test (PRIST)
A technique to assay serum immunoglobulin E (IgE) levels.
It resembles the radioimmunoabsorbent test except that
filter paper discs impregnated with anti-human IgE are used
in place of Sephadex ® discs.
papillomavirus immunity
Papillomaviruses induce skin and mucosa neoplasia.
Humans infected with this virus develop antibodies that
react with papillomavirus capsid proteins. Cervical cancer
patients frequently form antibodies against the E7 proteins
of HPV 16 and HPV 18. Patient sera have also demonstrated
antibodies against E2, E6, and E7 proteins. Chronic
infection in immunologically competent hosts points to the
possibility that the viral antigens may not be recognized
by the immune system. Human papillomavirus (HPV)
disease occurs in immunosuppressed transplant patients
and in patients with acquired immune deficiency syndrome
(AIDS). Thus, cell-mediated immunity is significant for
the control of HPV infection. Natural killer (NK) cells are
significant in the cellular response to HPV infection. NK
cell activity is decreased in patients with HPV-induced neoplasia.
Decreased numbers of the potent antigen-presenting
cells known as Langerhans’ cells occur in HPV precancerous
lesions. Viral antigens are presented to T lymphocytes
via major histocompatibility complex (MHC) class I
molecules that are downregulated in HPV-induced cervical
lesions. The papillomavirus evades the immune system
through downregulation of MHC class I molecules and
Langerhans cells and diminished susceptibility to NK cells.
Vaccines have been developed in animal models, especially
cpm
Anti-IgE IgE to be tested
Paper radioimmunosorbent test (PRIST).
TEST
Test sample
cattle. Therapeutic vaccines for subjects already infected
with these viruses hold promise.
papovavirus
Minute tumor viruses that are icosahedral and contain doublestranded
DNA. Included in the group are SV40 and polyomavirus
that may cause malignant and benign tumors. Permissive
or nonpermissive infections occur with papovavirus.
Following permissive infection of monkey cells, papovavirus
replicates, leading to lysis. T antigens—early papovavirus
proteins that occur in nonpermissive rodent cells—can lead
to transformation of the cells that is not reversible if the viral
genome is integrated into the host genome. It is reversible if
the cell can eliminate the viral genome.
parabiotic intoxication
The result of a surgical union of allogeneic adult animals.
The course of immune reactivity can be modified to take
a single direction by uniting parental and F 1 animals.
A hybrid recognizes parental cells as its own and does not
mount an immune response against them, but alloantigens
of F 1 hybrid cells stimulate the parental cells, leading to
graft-vs.-host disease.
para-Bombay phenotype
A variant Bombay phenotype of the ABO blood group
system. Individuals expressing it have Se secretor genes that
encode synthesis of blood groups A and B that are detectable
in secretions. However, these subjects do not produce
A and B erythrocytes as the H gene is absent. By comparison,
Bombay phenotype individuals do not have the H gene
or the enzyme it produces (fucosyl transferase) and do not
have A or B blood group substances on their erythrocytes
or in their secretions.
paracortex
A T lymphocyte, thymus-dependent area beneath and
between lymph node cortex follicles.
paracrine
Local effects of a hormone acting on cells in its immediate
vicinity.
paracrine factor
A molecule that produces its effect on cells in close proximity
to those that synthesize the factor. Powerful cytokine
molecules act in this way.
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