A mutant human T-cell line producing immunosuppressive factor(s)

Area of Science:

• Immunology
• Cell Biology

Background:

• Human T-cell line CEM-derived 6T-CEM-20 secretes a potent immunosuppressive factor.
• This factor specifically targets T cells, inhibiting various immune functions non-cytotoxically.

Purpose of the Study:

• To characterize the immunosuppressive factor secreted by 6T-CEM-20 cells.
• To investigate the mechanism and properties of this T-cell specific suppressor factor.

Main Methods:

• Cell-free supernatant from 6T-CEM-20 was used to assess T-cell suppression.
• Assays included mitogen-activated T-cell proliferation, cytotoxic T-cell functions, and pokeweed mitogen-stimulated plaque-forming cells.
• Preliminary purification via column chromatography and coculture experiments were performed.

Main Results:

• The supernatant potently suppressed T-cell proliferation and function via a non-cytotoxic mechanism.
• Suppressive activity was dependent on the dilution and timing of factor addition.
• The active factor is heat-sensitive, pH-sensitive, and has a high molecular weight (>200,000).
• Exposure to the factor induced T lymphocytes to suppress allogeneic T-cell proliferation.

Conclusions:

• A novel T-cell specific immunosuppressive factor, termed suppressor-activating factor (SAF), has been identified.
• SAF may function by activating suppressor T cells or inducing suppressor factor production.
• Further research is needed to elucidate SAF's molecular structure and detailed mechanism of action.