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Mutants in signal transduction through the T-cell antigen receptor
1Division of Tumor Virology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, Massachusetts 02115.
Abstract:
Mutants of an untransformed helper T-cell clone have been derived by chemical mutagenesis followed by selection for cells incapable of proliferating in response to antigen or anti-CD3. The selection was designed to enrich cells bearing mutations distal to the T-cell antigen receptor. The mutants express normal levels of functional T-cell receptors but are uncoupled from cellular responses, including gene induction, lymphokine secretion, proliferation, and phosphatidylinositol turnover. Responses to phorbol ester plus calcium ionophore and to interleukin-2 are unimpaired. Responses to antigen were restored by fusion with a T-cell receptor-negative thymoma, making the mutants valuable for investigating the mechanisms that couple T-cell receptor stimulation to the induction of second messengers and subsequent physiologic responses.
Insights
Researchers created T-cell mutants lacking normal responses to antigen stimulation. These cells, defective in T-cell receptor signaling, are crucial for understanding how T-cell receptor activation triggers downstream cellular events.
Area of Science:
- Immunology
- Cell Biology
- Molecular Biology
Background:
- Helper T-cells play a critical role in adaptive immunity.
- T-cell receptor (TCR) signaling is essential for T-cell activation and function.
- Understanding TCR signal transduction is key to immune response regulation.
Purpose of the Study:
- To generate and characterize T-cell mutants with defects in TCR signaling pathways.
- To investigate the molecular mechanisms coupling TCR stimulation to cellular responses.
- To identify components downstream of the TCR involved in signal transduction.
Main Methods:
- Chemical mutagenesis of a helper T-cell clone.
- Selection for cells unresponsive to antigen or anti-CD3 stimulation.
- Assessing cellular responses including proliferation, gene induction, and lymphokine secretion.
- Evaluating responses to phorbol ester/ionophore and IL-2.
- Complementation analysis via cell fusion.
Main Results:
- Mutants with functional TCRs but uncoupled signaling pathways were generated.
- These mutants showed impaired responses in gene induction, proliferation, and phosphatidylinositol turnover.
- Responses to phorbol ester/ionophore and IL-2 remained intact.
- Antigen responsiveness was restored upon fusion with TCR-negative cells.
Conclusions:
- The generated mutants are valuable tools for dissecting TCR signal transduction.
- These findings highlight specific defects in the signaling cascade distal to the TCR.
- Further investigation of these mutants will elucidate mechanisms of T-cell activation and second messenger induction.