CD40 activation is highly effective in generating large numbers of CD40-activated B cells that express high levels of MHC and costimulatory molecules. (A) Overall expansion of CD40-activated B cells from 8 different persons. CD40-activated B cells were generated by the coculture of PBMCs from 5 mL of peripheral blood with CD40L-transfected NIH3T3 (t-CD40-L) cells. (B) sCD40-L is as efficient as t-CD40-L cells at expanding human B cells in culture. CD40-activated B cells were generated by t-CD40-L cells or different concentrations of soluble hexameric CD40-L. The results shown are representative of 3 independent experiments. (C) Expression of CD80, CD86, and MHC class I and II on the CD40-activated B cells cultured for 8 days (solid histograms). The filled histograms were obtained with relevant isotype controls. Data shown here are representative of B-cell populations obtained from 8 different healthy adult donors.