Costimulatory signal provided by a B-lymphoblastoid cell line and its Ia-negative variant

Area of Science:

• Immunology
• Cell Biology

Background:

• Resting murine CD4+ T lymphocytes require specific signals for activation.
• Activation can be mediated by lectins like Concanavalin A (Con A) or antibodies targeting CD3 and Thy-1 molecules.

Purpose of the Study:

• To analyze the costimulatory requirements for activating murine CD4+ T lymphocytes.
• To investigate the role of B-lymphoblastoid cell lines as antigen-presenting cells.
• To explore methods for screening monoclonal antibodies affecting T cell function.

Main Methods:

• Activation of highly purified, resting murine CD4+ T lymphocytes.
• Use of B-lymphoblastoid cell lines (M12 and M12.C3) for costimulation.
• Paraformaldehyde fixation of cells to assess molecule expression.
• Generation of syngeneic mixed lymphocyte reactions.
• Screening of monoclonal antibodies using CD4+ T cell-M12.C3 interactions.

Main Results:

• Both Ia-positive (M12) and Ia-negative (M12.C3) B-lymphoblastoid cell lines provide necessary costimulatory activity for T cell activation.
• Costimulatory function is retained after paraformaldehyde fixation, indicating constitutive cell surface expression.
• Differences were observed between M12 cells and syngeneic antigen-presenting cells in mixed lymphocyte reactions.
• The CD4+ T cell-M12.C3 interaction is effective for screening monoclonal antibodies.

Conclusions:

• B-lymphoblastoid cell lines can serve as effective sources of costimulatory signals for CD4+ T cell activation.
• Constitutive expression of costimulatory molecules on the cell surface is demonstrated.
• The M12.C3 cell line provides a valuable tool for identifying and characterizing monoclonal antibodies impacting T cell function.