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Suppressive mechanisms in alloantigen-induced T cell responses
The Journal of Experimental Medicine
|December 1, 1983
Summary
Suppression of the mixed lymphocyte response (MLR) by MLR-TsF involves post-IL-2 receptor binding defects and a late-acting suppressor cell (Ts2). These mechanisms, independent of IL-2 availability, highlight late events in the IL-2 cascade.
Area of Science:
- Immunology
- Cellular immunology
- T cell activation
Background:
- The mixed lymphocyte response (MLR) is a key model for studying T cell activation and immune regulation.
- Mixed Lymphocyte Reaction-T Suppressor Factor (MLR-TsF) is known to suppress the MLR.
- The precise mechanisms by which MLR-TsF mediates suppression, particularly concerning Interleukin-2 (IL-2) regulation, require elucidation.
Purpose of the Study:
- To investigate whether MLR-TsF-mediated suppression results from interference with IL-2 regulation of T cell proliferation.
- To differentiate between direct effects of MLR-TsF on responder T cells and its capacity to induce suppressor cells (Ts2).
- To determine the stage of T cell activation affected by MLR-TsF and its Ts2-inducing activity.
Main Methods:
- Assessing the effect of exogenous IL-2 on MLR-TsF-induced suppression.
- Analyzing IL-2 receptor expression and function on responder T cells.
- Evaluating the proliferation of IL-2-dependent cell lines (HT2 cells) and MLR-activated cells under MLR-TsF influence.
- Characterizing the kinetics and IL-2 dependency of Ts2 cell activity.
Main Results:
- MLR-TsF-induced suppression is not abrogated by exogenous IL-2, indicating a post-IL-2 binding defect.
- Responder T cells in suppressed cultures express functional IL-2 receptors.
- MLR-TsF directly inhibits IL-2-driven proliferation at a postreceptor level.
- A late-acting Ts2 cell is induced, with partial IL-2 sensitivity, but its major suppressive component is IL-2 resistant.
- IL-2 production remains normal in Ts2-regulated cultures.
Conclusions:
- MLR-TsF-mediated suppression involves a postreceptor defect in responder T cell proliferation, distinct from IL-2 availability or receptor acquisition.
- The induction of a late-acting, largely IL-2-independent Ts2 cell contributes significantly to suppression.
- Alloantigen-induced suppression ultimately involves late events within the IL-2-dependent lymphokine cascade.