Plaque-forming cells in human cord blood: a soluble factor suppressing differentiation but not proliferation of B cells.

Cord blood-derived T cells have been shown to suppress differentiation of B cells into immunoglobulin-secreting cells and proliferation of mononuclear cells (MNC). We report about a soluble factor present in the supernatant of pokeweed mitogen (PWM)-stimulated cord blood MNC which was able to suppress significantly the number of plaque-forming cells (PFC) in adult MNC populations, but had no effect upon proliferation of adult MNC in response to PWM and allogeneic MNC. The number of PFC was not suppressed by supernatant from unstimulated cord blood MNC or by PWM-stimulated adult MNC.