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pathogenesis-related (PR) proteins 560 PCNA
broadly expressed by microbial pathogens not found on host
tissues. Ligands for pattern recognition molecules (PRMs).
The pattern-recognition receptors (PRRs) of the immune
system use PAMPs to differentiate between pathogen antigens
and self antigens.
pathogenesis-related (PR) proteins
Products of plant cells manifesting local acquired resistance.
These substances include chitinases, P1,3 glucanases,
peroxidases, RNases, proteases and enzyme inhibitors. These
PR proteins break down pathogen constituents to yield small
degradation products that initiate further plant responses.
pathogenicity
The capacity of a microorganism to induce disease. Factors
that contribute to pathogenicity include toxin production,
activation of host inflammatory responses, and perturbation
of host cell metabolism.
pathologic autoantibodies
Autoantibodies generated against self antigens that induce
cell and tissue injury following interaction with the cells
bearing epitopes for which they are specific. Many autoantibodies
are physiologic, representing an epiphenomenon during
autoimmune stimulation, whereas others contribute to
the pathogenesis of tissue injury. Autoantibodies that lead to
red blood cell destruction in autoimmune hemolytic anemia
represent pathogenic autoantibodies, whereas rheumatoid
factors such as IgM anti-IgG autoantibodies have no proven
pathogenic role in rheumatoid arthritis.
pathology
The study of disease.
pattern recognition molecules (PRMs)
Protein molecules that identify pathogen-associated
molecular patterns. They may be soluble or membranebound.
Collectins, including MBL, acute phase proteins,
NOD proteins, and natural antibodies comprise the soluble
PRMs. Those that are membrane-bound are termed pattern
recognition receptors (PRRs).
pattern recognition receptors (PRRs)
Receptors that bind to pathogen-associated molecular
patterns (PAMPs). Natural or innate immune system
receptors that recognize molecular patterns comprising
frequently encountered structures produced by microorganisms.
These receptors enhance natural immune responses
against microbes. CD14 receptors on macrophages that bind
bacterial endotoxin to activate macrophages and the mannose
receptor on phagocytes that bind microbial glycoproteins or
glycolipids are examples of PRRs. These plasma membrane
or endocytic vesicle membrane-bound pattern recognition
molecules have a broad distribution pattern. Toll-like
receptors, NK activatory receptors, γδ T cell receptors, and
the NKT semi-invariant TCR also belong to this category
of molecules. Binding of PRRs leads to proinflammatory
cytokine expression.
Paul–Bunnell test
An assay for heterophile antibodies in patients with infectious
mononucleosis. It is a hemagglutination test in which
patient serum induces sheep red blood cell agglutination.
Absorption of the serum with guinea pig kidney tissue
removes antibody to the Forssman antigen but does not
remove the sheep red blood cell agglutinin that can be
absorbed with ox cells. This hemagglutinin is distinct from
antibodies against the causative agent of infectious mononucleosis
(i.e., the Epstein–Barr virus).
Linus Pauling.
Pauling, Linus (1901–1994)
Nobel Laureate in chemistry and proponent of the template
theory of antibody formation that was championed
by immunochemists.
Pax-5 gene
DNA that encodes B cell-specific activator protein
(BSAP) required as a transcription factor for B lymphocyte
development.
Rose Payne.
Payne, Rose (1909–1999)
A pioneer in human histocompatibility.
PBC
Abbreviation for primary biliary cirrhosis.
PCA
Abbreviation for passive cutaneous anaphylaxis.
PCH
Abbreviation for paroxysmal cold hemoglobinuria.
PCNA
Proliferating cell nuclear antigen (PCNA), which is a 29-kDa
protein present mainly in dividing cells. Also called cyclin.