coated magnetic beads dynal oslo sweden at the onset of stimulation 2 u00d7 10 5 peptide loaded dc and 2 u00d7 10 6 responder cells were co cultured per well of a 24 well tissue culture plate costar badhoevedorp the netherlands in 2 ml of iscoves medium containing 5 pooled human ab serum 10 3 u ml il 6 sandoz basel switzerland and 5 ng ml il 12 on day 8 and day 15 the responder populations were restimulated using peptide pulsed dendritic cells as stimulator cells the cultures were propagated in medium containing il 2 cetus corp emeryville calif and il 7 genzyme cambridge mass at final concentrations of 10 u ml and 5 ng ml respectively weekly hereafter the cultures were restimulated using adherent peptide pulsed pbmc as was described previously bakker et al 1995 cancer res 55 5330 responder populations were tested for specific lytic activity after at least 4 rounds of restimulation chromium release assays were performed as described previously bakker et al 1994 j exp med 179 1005 briefly 10 6 target cells were incubated with 100 mci na 2 51 cro 4 amersham bucks uk for 1 hour various amounts of effector cells were then added to the target cells in.