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protoplast fusion 600 pseudoallergic reaction
hypertonic media for survival. They do not usually multiply.
The hypertonic solution protects them from lysis. Protoplasts
can also be produced from Gram-positive bacteria by treatment
with penicillin or other antibiotics that inhibit cell wall
synthesis. Gram-negative bacteria have cell walls composed
of a thin peptidoglycan layer enclosed by an exterior
membrane of lipopolysaccharide. Protoplasts prepared from
Gram-negative bacteria are frequently termed spheroplasts.
protoplast fusion
A technique for DNA transfer from one group of bacteria to
others, to myeloma cells, or to other animal cells in culture.
The exposure of plasmid-bearing Escherichia coli microorganisms
to lysozyme and EDTA yields protoplasts that
may be fused with myeloma cells by polyethylene glycol
treatment.
protostomes
Animals arising from coelomates that developed into
higher invertebrates.
protozoa
Microscopic animals that must recognize and eat food.
Intricate genetic mechanisms control their surface proteins.
protozoans
Single-celled parasites.
proviral DNA
Refer to provirus.
provirus
The DNA version of a retrovirus integrated into a host cell
genome where it may remain inactive transcriptionally for
prolonged periods.
provocation poliomyelitis
An uncommon consequence of attempted immunization
against poliomyelitis in which paralysis quickly followed
injection of vaccines such as those that contained
Bordetella pertussis or alum.
prozone
In agglutination and precipitation reactions, the lack of agglutination
or precipitation in tubes where the antibody concentration
is greatest attributable to suboptimal agglutination or
precipitation in the region of antibody excess. Agglutination or
precipitation becomes readily apparent in the tubes where the
same antibody is more dilute. This is known as a prozone or
prozone phenomenon. It is attributable to a blocking antibody
or antibody combining with individual cells or molecules,
as in antibody excess, or to a serum lipid- or protein-induced
nonspecific inhibition reaction. Soluble complexes of antigen
and antibody may be present in the antibody excess zones of
Tube no.
Serum
dilution
Agglutination
certain precipitation reactions. Excess antibody coating the
surfaces of cells in an agglutination reaction in the antibody
excess zone may prevent cross linking, which is requisite for
agglutination to become manifest. The prozone represents a
false-negative reaction. When a serum sample is believed to
contain a certain antibody that is masked or demonstrates a
prozone phenomenon, the sample must be diluted serially to
demonstrate reactivity in more dilute tubes to avoid reporting a
false-negative result.
prozone effect
Refer to prozone.
PRP antigen
Polyribosylribitol capsular polysaccharide; an antiphagocytic
cell wall constituent of Hemophilus influenzae that provides the
microorganism with an effective mechanism to induce disease.
Type-specific antibodies that facilitate immunization are requisite
for protective immunity against H. influenzae. Children
under 2 years old are poor producers of anti-PRP antibodies,
making them more susceptible to the infection.
PRP-D
Polyribosylribitol–diphtheria toxoid. Refer to Hib.
pruritis
Severe itching.
PSA
Refer to prostate-specific antigen.
pSMAC
Peripheral supramolecular activation complex. The interior
pSMAC encircles the cSMAC and accommodates CD2/
LFA-3 pairs. The exterior pSMAC encircles the inner
pSMAC, accommodates LFA-1/ICAM-1 pairs, and is
united to the actin cytoskeleton.
P-selectin
A molecule found in the storage granules of platelets and the
Weibel–Palade bodies of endothelial cells. Ligands are sialylated
Lewis X and related glycans. P-selectins are involved
in the binding of leukocytes to endothelium and platelets to
monocytes in areas of inflammation. Also called CD62P.
pseudoalleles
Genes that are closely linked but distinct. They have
functional similarity and act as alleles in complementation
investigations; crossover studies may separate them.
pseudoallergic reaction
A nonimmunological clinical syndrome characterized by signs
and symptoms that mimic or resemble immune-based allergic
or immediate hypersensitivity reactions; these reactions are not
mediated by specific antibodies or immune lymphoid cells.
1 2 3 4 5 6
1:8
1:16 1:32 1:64 1:128 1:256
0 0 0 + + +
Prozone effect.