Related Experiment Videos
Dendritic cells in antitumor immune responses. I. Defective antigen presentation in tumor-bearing hosts
D I Gabrilovich1, I F Ciernik, D P Carbone
1Simmons Cancer Center, University of Texas Southwestern Medical Center, Dallas 95235-8593, USA. dgabrilovich@simmons.swmed.edu
Abstract:
Induction of specific antitumor cytotoxic T cell responses was studied in BALB/c mice bearing tumors transfected with a mutant human p53 minigene. We observed that mice were resistant to the induction of peptide-specific CTL as early as 5 days after challenge with a minimal lethal dose of tumor cells, and the cell types responsible for this effect were further characterized. The contribution of CD4+ and CD8+ T cells in this response was studied after peptide-pulsed dendritic cell (DC) immunization. In vitro depletion of CD4+ cells during peptide restimulation reduced the level of specific lysis in control mice, and depletion of CD8+ T cells completely abrogated it. Substitution of CD8+ cells from immunized control mice during restimulation of cells from immunized tumor-bearing mice did not change the level of specific lysis. Substitution of the CD4+ from tumor-bearing mice by CD4+ cells from control mice improved CTL response, although this response did not reach control values. Peptide-pulsed dendritic cells isolated from tumor-bearing mice showed a significantly reduced ability to induce specific CTL in control animals and reduced ability to restimulate immune T cells from control mice in vitro. DC from tumor-bearing mice also had a reduced ability to stimulate control allogeneic T cells. Restimulation of T cells from immunized tumor-bearing mice with DC from control animals, but not from tumor-bearing mice, dramatically increased specific CTL responses to control levels. Macrophages at the same concentration were not able to improve CTL function. Thus, defective antigen presentation by DC appears to be a major determinant for CTL nonresponsiveness to peptide antigens in tumor-bearing mice, and addition of control DC can restore specific lysis. These data provide a basis for new approaches to peptide-based cancer immunotherapy.
Insights
Tumor-bearing mice resist cytotoxic T lymphocyte (CTL) responses due to defective antigen presentation by dendritic cells (DCs). Supplementing with healthy DCs restores CTL activity, offering new avenues for peptide-based cancer immunotherapy.
Area of Science:
- Immunology
- Cancer Biology
- Cellular Immunology
Background:
- Cytotoxic T lymphocytes (CTLs) are crucial for antitumor immunity.
- Tumor progression can lead to immune evasion and T cell dysfunction.
- Dendritic cells (DCs) play a pivotal role in initiating T cell responses.
Purpose of the Study:
- To investigate the mechanisms underlying resistance to CTL induction in tumor-bearing mice.
- To characterize the role of CD4+ and CD8+ T cells in antitumor responses.
- To evaluate the function of dendritic cells in tumor-induced immune suppression.
Main Methods:
- Tumorigenesis model in BALB/c mice with a mutant p53 minigene.
- Peptide-pulsed dendritic cell immunization and in vitro T cell depletion assays.
- Assessment of CTL activity and antigen presentation capacity of dendritic cells.
Main Results:
- Tumor-bearing mice showed resistance to peptide-specific CTL induction.
- Defective antigen presentation by tumor-associated dendritic cells was identified as a key factor.
- Restoring functional dendritic cells reversed T cell nonresponsiveness and enhanced CTL activity.
Conclusions:
- Defective dendritic cell function is a major cause of CTL nonresponsiveness in tumor-bearing hosts.
- Enhancing dendritic cell-mediated antigen presentation is a promising strategy for peptide-based cancer immunotherapy.
- These findings support the development of novel immunotherapeutic approaches targeting the tumor microenvironment.