Rosette-increasing factor released by PHA-stimulated mononuclear cells in vitro which augments active E and EA...

Area of Science:

• Immunology
• Cell Biology

Background:

• Phytohaemagglutinin (PHA) stimulates mononuclear (MN) cells.
• Active E and EA (IgG) receptor-forming cells (RFC) are linked to cell-mediated immunity.

Purpose of the Study:

• To identify and characterize a factor in PHA-stimulated mononuclear cells that influences RFC levels.
• To investigate the cellular origin and stability of this factor.

Main Methods:

• Stimulation of mononuclear cells with phytohaemagglutinin (PHA).
• Assay of cell-free supernatants for rosette-increasing factor (RIF) activity.
• Pretreatment of cells with cycloheximide, cytochalasin B, mitomycin C, and colchicine.

Main Results:

• A factor, termed rosette-increasing factor (RIF), was found in PHA-stimulated mononuclear cell supernatants.
• RIF significantly increased active E and EA (IgG) RFC, primarily T cells.
• RIF production was mainly by nylon wool-adherent T cells and independent of macrophages.
• RIF activity was abolished by cycloheximide and cytochalasin B but unaffected by mitomycin C and colchicine.

Conclusions:

• The rosette-increasing factor (RIF) is produced by T cells and enhances specific RFC populations.
• RIF stability and production kinetics suggest a role in cellular immune responses.
• Understanding RIF may offer insights into modulating cellular immunity.