While performing intracellular cytokine assay on B cells, I am finding a peculiar population. I use 2*10^6 cells for studying each functional marker. The pbmcs are cultured for 72 hours, with CD40L dose being given in 0 hour after plating and BFA in the 48th hour. When analysed, I am getting two CD19+ populations from the lymphocytes. Can anyone enlighten me about what actually is happening?