Dye efflux by myeloma B cells is comparable to that of normal resting B cells and higher than that of stimulated normal B cells. Each dot represents one blood sample. Normal B cells were from heathy adult volunteers. Activated B cells were from healthy donors and their dye efflux was measured after stimulation in vitro with phytohemaglutinin or pokeweed mitogen for 3 to 5 days as previously described.34 Values are mean ± SE.