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positive induction apoptosis 585 post-streptococcal glomerulonephritis
Rodney Robert Porter.
Paul Jules Portier.
HLA molecules on allogeneic donor cells in the blood of a
transplant recipient.
positive induction apoptosis
Two central pathways lead to apoptosis: (1) positive induction
by ligand binding to plasma membrane receptor; and (2)
negative induction by loss of suppressor activity. Each leads
to activation of cysteine proteases with homology to IL1β
converting enzymes (ICEs or caspases). Positive induction
involves ligands related to TNF. Ligands are typically
trimeric and bind to cell surface receptors causing aggregation
(trimerization) of cell surface receptors. Receptor
oligomerization orients their cytosolic death domains into
a configuration that recruits adaptor proteins. The adaptor
complex recruits caspase-8. Caspase-8 is activated, and the
cascade of caspase-mediated disassembly proceeds.
positive selection
Pathway in the thymus that promotes the survival of
immature T cells with receptors that recognize self
peptide complexed to self MHC with only low affinity/
avidity, i.e., those with the greatest capacity to identify
nonself peptide complexed to self MHC with high affinity.
Positively selected cells are the only ones permitted to
continue their maturation. The resulting cell population is
self MHC-restricted and capable of interacting with both
self and foreign antigens. NKT cells are also subjected
to positive selection in the thymus. It is unclear whether
developing B cells with low affinity for self antigen
receive survival signals, i.e., are positively selected. Refer
to negative selection.
postcapillary venules
Relatively small blood vessels lined with cuboidal epithelium
through which blood circulates after it exits capillaries
and before it enters veins. They are frequent sites of migration
of lymphocytes and inflammatory cells into tissues
during inflammation. Recirculating lymphocytes migrate
from the blood to lymph through high endothelial venules
of lymph nodes.
post-cardiotomy syndrome
A condition that follows heart surgery or traumatic injury.
Autoantibodies against heart antigens may be demonstrated
by immunofluorescence within weeks of the surgery or
trauma. Corticosteroid therapy represents an effective
treatment. Patients suffering myocardial infarcts may also
develop a similar condition.
post-GC
Designation for a leukemia/lymphoma in which the transformed
cells express an activated B cell or memory B cell
phenotype. There is a high frequency of somatic hypermutations
in the genome.
post-infectious encephalomyelitis
Demyelinating disease following a virus infection that is
mediated by autoimmune delayed-type (type IV) hypersensitivity
to myelin.
post-infectious iridocyclitis
Inflammation of the iris and ciliary body of the eye. This
may occur after a virus or bacterial infection and is postulated
to result from an autoimmune reaction.
post-rabies vaccination encephalomyelitis
A demyelinating disease produced in humans actively
immunized with rabies vaccine containing nervous system
tissue to protect against the development of rabies. Serial
injections of rabbit brain tissue containing rabies virus
killed by phenol may induce demyelinating encephalomyelitis
in a recipient. This method of vaccination was
replaced with a vaccine developed in tissue culture that did
not contain any nervous tissue.
post-streptococcal glomerulonephritis
An acute proliferative glomerulonephritis that may
follow a streptococcal infection of the throat or skin by 1
to 2 weeks. It is usually seen in 6- to 10-year old children,
but may occur in adults as well. The onset is heralded
by acute nephritis. Ninety percent of patients have been
infected with group A β hemolytic streptococci that are
nephritogenic— specifically, types 12, 4, and 1, that are
revealed by their cell wall M protein. Poststreptococcal
glomerulonephritis is mediated by antibodies induced by
the streptococcal infection. Most patients show elevated
antistreptolysin-O (ASO) titers. Serum complement levels
are decreased. Immunofluorescence of renal biopsies
demonstrates granular immune deposits that contain
immunoglobulin and complement in the glomeruli.
This finding is confirmed by electron microscopy. The
precise streptococcal antigen has never been identified;
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