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CD8 functions as an inhibitory ligand in mediating the immunoregulatory activity of CD8+ cells
J E Hambor1, D R Kaplan, M L Tykocinski
1Institute of Pathology, Case Western Reserve University, Cleveland, OH 44106.
Insights
The CD8 molecule can act as an inhibitory ligand, not just a receptor, regulating immune responses. This CD8-dependent inhibition affects T cells during primary antigen stimulation, offering new therapeutic possibilities.
Area of Science:
- Immunology
- Molecular Biology
- Cell Biology
Background:
- The CD8 molecule is traditionally viewed as a receptor on T cells.
- Its precise role in immunoregulation, particularly in inhibitory functions, requires further elucidation.
Purpose of the Study:
- To investigate the physiological requirements for CD8-dependent immunoregulation.
- To explore the potential of CD8 as an inhibitory ligand.
Main Methods:
- Utilized antisense and sense transfection technologies in cellular coculture systems.
- Examined genetically engineered CD8 molecules with glycoinositolphospholipid anchors and fixed natural CD8 molecules.
Main Results:
- Demonstrated that CD8 molecules, both engineered and natural (fixed), exhibit CD8-dependent immunoregulatory activity.
- Showed that CD8-dependent inhibition induces nonresponsiveness in antigen-specific responders for at least 24 hours.
- Identified that only cells undergoing primary, not secondary, T cell receptor (TCR) stimulation are susceptible to CD8-dependent inhibition.
- Confirmed inhibition of both CD4+ and CD8+ T cells by CD8+ modulatory cells.
Conclusions:
- Established that CD8 can function as an inhibitory ligand, expanding its known roles.
- Provided foundational data for developing artificial CD8-based immunomodulatory peptides.
- Aimed to deepen the understanding of CD8's role in natural immunoregulation.
Abstract:
Antisense and sense transfection technologies were employed in cellular coculture systems to investigate the physiologic requirements for CD8-dependent immunoregulation. Our data indicate that cells bearing genetically engineered CD8 molecules incorporating a glycoinositolphospholipid membrane anchor, as well as fixed cells bearing natural CD8 molecules, retain specific, CD8-dependent immunoregulatory activity. These findings together support the novel concept that CD8, a molecule traditionally thought of as a receptor, can function as an inhibitory ligand. CD8-dependent inhibition was shown to induce nonresponsiveness, persisting for at least 24 h, in Ag-specific responders. Moreover, only cells undergoing primary, but not secondary, antigenic stimulation through their TCR were found to be susceptible to CD8-dependent inhibition. Both CD4+ and CD8+ responding T cells were inhibited by CD8+ modulatory cells. These functional analyses of inhibitory and responder cells in CD8-dependent inhibition lay the groundwork for developing artificial CD8-based immunomodulatory peptides and deciphering CD8's role in natural immunoregulation.