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Epitopes and functional responses defined by a panel of anti-Fas (CD95) monoclonal antibodies
1Department of Pediatrics, Mie University School of Medicine, Tsu, Japan. komada@clin.medic.mie-u.ac.jp
Abstract:
Fas (CD95) is a cell surface glycoprotein that mediates apoptotic cell death when cross-linked with agonistic anti-Fas monoclonal antibodies (MAbs) or the endogenous Fas ligand. In this study, we investigated the in vitro biological properties of a panel of anti-human Fas MAbs. We found that five anti-Fas MAbs of IgG1 subclass (B.E28, B.G30, B.L25, DX2, and B.G34) induced marked apoptotic cell death in Fas-expressing leukemia cells, although this killing was delayed when compared to the cytolytic effect mediated by the prototypic anti-Fas MAb of IgM subclass (clone CH-11). On the other hand, four clones (ZB4, B.G27, B.D29, and B.K14) efficiently blocked apoptotic cell death induced by the CH-11 MAb or Fas ligand. The ability of these MAbs to inhibit cell death appeared to correlate with their relative affinity for the Fas molecule. Furthermore, different clones recognized the same epitope and elicited different effects (induction or inhibition of cell killing); conversely, different clones elicited the same effect but recognized different epitopes. These results suggest that the different biological effects of anti-Fas MAbs would not be mediated in an epitope-restricted manner. The relative binding affinity might correlate to some extent with the biological properties of the MAb.
Insights
Researchers studied anti-Fas monoclonal antibodies (MAbs) for their ability to induce or block apoptosis. While some MAbs triggered cell death, others inhibited it, suggesting binding affinity, not just epitope recognition, influences biological effects.
Area of Science:
- Immunology
- Cell Biology
- Molecular Biology
Background:
- Fas (CD95) is a cell surface receptor crucial for initiating apoptosis (programmed cell death).
- Cross-linking Fas with agonistic antibodies or Fas ligand triggers apoptotic signaling pathways.
- Dysregulation of Fas-mediated apoptosis is implicated in various diseases, including cancer and autoimmune disorders.
Purpose of the Study:
- To investigate the in vitro biological properties of a panel of anti-human Fas monoclonal antibodies (MAbs).
- To determine if anti-Fas MAbs can induce or inhibit Fas-mediated apoptotic cell death.
- To explore the relationship between MAb binding affinity, epitope recognition, and biological function.
Main Methods:
- In vitro assessment of anti-Fas MAbs' ability to induce apoptosis in Fas-expressing leukemia cells.
- Evaluation of MAbs' capacity to block apoptosis induced by a prototypic anti-Fas MAb (CH-11) or Fas ligand.
- Analysis of MAb binding affinity to the Fas molecule.
- Characterization of epitope recognition patterns for different MAb clones.
Main Results:
- Five IgG1 anti-Fas MAbs induced significant apoptotic cell death in leukemia cells, though with a delayed onset compared to the IgM MAb CH-11.
- Four anti-Fas MAbs effectively inhibited CH-11 MAb or Fas ligand-induced apoptosis.
- Inhibitory MAb efficacy correlated with their binding affinity for Fas.
- Different MAbs recognizing the same epitope showed varied effects (induction vs. inhibition), while MAbs with similar effects recognized different epitopes.
Conclusions:
- The biological effects of anti-Fas MAbs are not solely determined by epitope specificity.
- Relative binding affinity appears to be a significant factor influencing the functional properties of anti-Fas MAbs.
- These findings have implications for developing targeted therapies involving Fas-mediated apoptosis.