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tumor-associated antigens 720 tumor immunotherapy
Class I
Class II
Class III
Normal
cells
TAA
Neoplastic
cells
tumor-associated antigens
Epitopes of selected tumor cells that are also found on
certain types of normal cells. They may be protein or
carbohydrate molecules expressed in abnormal concentration,
location, or time in a tumor cell compared with
expression in a healthy differentiated cell in the tissue of
origin. Normal cellular genes that have become dysregulated
encode tumor-associated antigens. Examples include
normal cellular proteins, differentiation antigens, tissue
type-specific antigens, embryonic antigens, and idiotypic
antigens. Certain antigens designated CA-125, CA-19-9, and
CA195, among others may be linked to certain tumors such
as lymphomas, carcinomas, sarcomas, and melanomas, but
the immune response to these tumor-associated antigens
is not sufficient to mount a successful cellular or humoral
immune response against the neoplasm. Three classes of
tumor-associated antigens have been described. Class 1
antigens are very specific for a certain neoplasm and absent
from normal cells. Class 2 antigens are found on related
neoplasms from separate individuals. Class 3 antigens are
Macrophage
Helper
T cell
TAA
TAA
TAA
Mast cell
Tc cell
Related
neoplastic cells
TNF-α
TNF-β
TAA
TAA
Tumor-associated antigens (TAAs) among normal and neoplastic cells.
found on malignant and normal cells but show increased
expression in neoplastic cells. Assays of clinical value will
probably be developed for class 2 antigens, as they are
associated with multiple neoplasms and are rarely found in
normal individuals.
tumor enhancement
The successful establishment and prolonged survival
(conversely, the delayed rejection) of a tumor allograft,
especially in mice, as a consequence of contact with specific
antibody.
tumor hypoxia
Diminished oxygen pressure that develops in parts of a
tumor that has outgrown its blood supply. Sensitivity to
radiation and chemotherapy become less effective as tumor
cells undergo hypoxia.
tumor imaging
An experimental and clinical technique employed to localize
neoplastic lesions using a labeled antibody or its fragment.
Tumor imaging is based on the presence of an antigen
expressed only on a tumor cell or exhibits a significant
difference in amount and/or distribution between tumor and
normal tissues.
tumor immunity
A number of experimentally induced tumors in mice
express numerous specific transplantation antigens that
can induce an immune response leading to the destruction
of neoplastic cells in vivo. Lymphocytes play a critical
role in the immunological destruction of many antigenic
tumors. Both cell-mediated and antibody-mediated immune
responses to human neoplasms have been identified and
their targets characterized in an effort to develop clinically
useful immunotherapy.
tumor immunotherapy
Immunological surveillance, first proposed by Paul
Ehrlich 100 years ago, is believed to be a protective
mechanism against the development of neoplasias in intact
healthy subjects. Significant suppression of the immune
system from any cause may favor tumor development.
Contemporary attempts at therapeutic modification of the
immune response include the use of immune response
Tumor cell
Tumor necrosis factor (TNF)-mediated immune reaction.
Tumor cell lysis