Polyclonal activation of bone-marrow-derived lymphocytes from human peripheral blood measured by a direct plaque-forming cell assay.

A culture and assay system for the stimulation of human peripheral blood lymphocytes with polyclonal activators of bone-marrow-derived lymphocytes (B cells), such as pokeweed mitogen and Escherichia coli lipopolysaccharide, and subsequent measurement of single cell antibody production by a hemolysis-in-bel direct plaque-forming cell assay against sheep erythrocytes has been established. The critical culture requirements have been delineated and a new highly sensitive ultrathin gel assay method has been described. Under these conditions a substantial and highly reproducible plaque-forming cell response was detected in normal human peripheral blood. This system can be readily used to explore the complex events associated with activation of human B cells.