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tumor necrosis factor (TNF) receptors 723 TUNEL-based assays
Type I
COOH
Type II
COOH
TNF receptors designated type I (CD120a) and type II (CD120b). Both the
55-kDa type I and the 75-kDa type II receptors bind TNF-α and TNF-β
(lymphotoxin). These receptors belong to the NGRF/TNFR superfamily.
Their extracellular domains contain four cysteine-rich repeats.
tumor necrosis factor (TNF) receptors
A receptor for tumor necrosis factor composed of 461amino
acid residues and an extracellular domain that is rich
in cysteine. Cell surface receptors for TNF-α and TNF-β
(LTα) are expressed by most cell types. Of the two TNF
receptors, TNF-RI mediates most biologic effects of TNF-N
(TNF-RII). TNF receptors possess cysteine-rich extracellular
motifs that include Fas and CD40. These receptors
have essentially no homology in their intracellular domains.
Tumor virus
particle
Tumor cell
Tumor-specific antigens (TSAS).* Each tumor induced by a
single virus will express the same TSA on the cell
surface despite the morphology of the cell.
Soluble types I and II have been described in urine and
serum. With the exception of erythrocytes and resting
T cells, TNF receptors are found on most types of cells.
Whereas the type I p55 receptor is widely distributed on
various cell types, the type II p75 receptor appears confined
to hematopoietic cells. The human p55 receptor contains
three potential N-linked glycosylation sites; the type II p75
form contains only two.
tumor promoter
Refer to phorbol esters.
tumor regression
A decrease in size or remission of a malignant tumor as a
consequence of anticancer therapy; regression may occur
spontaneously without treatment.
tumor rejection antigen
An antigen that is detectable when transplanted tumor cells
are rejected; also called tumor transplant antigen.
tumor-specific antigen (TSA)
An antigen present on tumor cells but not found on normal
cells. Murine tumor-specific antigens can induce transplantation
rejection in mice. Encoded by mutated cellular genes
or viral oncogenes.
tumor-specific determinants
Epitopes present on tumor cells and also identifiable in
varying quantities and forms on normal cells.
tumor-specific transplantation antigen (TSTA)
Epitopes that induce rejection of tumors transplanted
among syngeneic (histocompatible) animals.
tumor suppressor genes
Genes such as p53 and PTEN that encode cellular proteins
that prevent cells from becoming neoplastic; their absence
promotes carcinogenesis.
TUNEL assay (TdT-dependent dUTP–biotin
nick end labeling)
A technique that identifies apoptotic cells in situ by fragmentation
of their DNA. Immunohistochemical staining
with enzyme-linked streptavidin identifies biotin-tagged
dUTP added to the free 3′ ends of the DNA fragments by
the terminal deoxynucleotidyl transferase (TdT) enzyme.
TUNEL-based assays
DNA fragments can be stained in situ by using terminal
deoxynucleotidyl transferase (TdT) to polymerize labeled
nucleotides onto the ends of nicked DNA (TdT-dependent
Tumor-
specific
antigen
(TSA)*
T