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Pseudomonas exotoxin-anti-TAC. Cell-specific immunotoxin active against cells expressing the human T cell growth
Abstract:
An immunotoxin was constructed with an activity that discriminated between two T cell lines based on the expression of the T cell growth factor (TCGF) receptor on their cell surface. A toxic protein conjugate, designated PE-anti-TAC, was made by chemically coupling pseudomonas exotoxin (PE) to a monoclonal antibody (anti-TAC) that recognizes the human TCGF receptor. This conjugate was toxic to HUT-102 cells, a cell line that expresses the TCGF receptor, but was nontoxic for MOLT-4 cells, a receptor-negative line. The toxicity of PE-anti-TAC was enhanced 50-fold in the presence of human adenovirus type II and was reduced to control levels by adding excess anti-TAC antibody. The toxicity of PE-anti-TAC for HUT-102 cells was compared with PE-anti-transferrin receptor. To compare the route of entry for both anti-TAC and anti-TFR using electron microscopy, protein conjugates were made by coupling horseradish peroxidase (HRP) to each antibody. Anti-TFR-HRP entered HUT-102 cells by concentrative adsorptive endocytosis via coated pits, and the majority of the antibodies bound to the cell surface at 4 degrees C were seen in receptosomes by 10 min after warming to 37 degrees C. Anti-TAC-HRP was also found to enter HUT-102 cells via coated pits and receptosomes; but, in contrast to anti-TFR, anti-TAC did not selectively concentrate in coated pits, and therefore the majority of this surface-bound antibody were not internalized in HUT-102 cells by 10 min at 37 degrees C.
Insights
Researchers developed an immunotoxin targeting the T cell growth factor (TCGF) receptor for selective T cell toxicity. This PE-anti-TAC conjugate showed enhanced activity with adenovirus, offering a targeted approach for T cell therapies.
Area of Science:
- Immunology
- Molecular Biology
- Cell Biology
Background:
- T cell growth factor (TCGF) receptor expression varies on T cell lines.
- Targeting specific cell surface receptors is a strategy for selective cell manipulation.
- Immunotoxins combine cytotoxic agents with receptor-specific antibodies.
Purpose of the Study:
- To construct and characterize an immunotoxin (PE-anti-TAC) targeting the TCGF receptor.
- To evaluate the selective toxicity of PE-anti-TAC against T cell lines.
- To investigate the cellular uptake mechanisms of anti-TCGF receptor and anti-transferrin receptor antibodies.
Main Methods:
- Chemical coupling of Pseudomonas exotoxin (PE) to anti-TCGF receptor antibody (anti-TAC).
- Assessing conjugate toxicity on TCGF receptor-positive (HUT-102) and negative (MOLT-4) T cell lines.
- Electron microscopy of horseradish peroxidase (HRP)-conjugated antibodies to study cellular entry pathways.
Main Results:
- PE-anti-TAC demonstrated selective toxicity towards HUT-102 cells, sparing MOLT-4 cells.
- Toxicity was significantly enhanced by human adenovirus type II and blocked by excess anti-TAC.
- Anti-transferrin receptor (anti-TFR) internalized via concentrative adsorptive endocytosis, while anti-TAC showed less selective concentration in coated pits.
Conclusions:
- PE-anti-TAC is a potent and selective immunotoxin targeting the TCGF receptor.
- Adenovirus enhances immunotoxin activity, suggesting potential synergistic therapeutic strategies.
- Differential internalization pathways of anti-TAC and anti-TFR highlight receptor-specific cellular trafficking.
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