Leukemic cells up-regulate costimulatory molecules upon IL-3 and CD40L activation.

Expression of APC-related molecules on fresh and cultured leukemic cells were shown in patient GEN and GUE CD40, CD80, and CD86 that were either not expressed or were present at a low level on fresh cells (upper panels) were up-regulated after a 6-day culture with IL-3 (middle panels). HLA molecules that were already present on fresh cells were also up-regulated. Addition of CD40L-transfected L cells during the last 48 hours of culture further increased the expression of these molecules (lower panels). Open curves show isotype control; shaded curves show specific staining. Results are representative of 5 experiments of culture with IL-3. Mean fluorescence intensity ratios between specific mAb and isotypic control are indicated in the plot.