Schematic overview of the combined IMS and RT-PCR analysis. 1) Fresh lymph nodes were disintegrated in sterile PBS. The resulting cell suspension was filtered, centrifuged, diluted in PBS and aliquoted. The cells were then mixed with either MOC31 coated magnetic beads (anti-EpCAM), BM-7 coated magnetic beads (anti-Mucin 1) or beads without antibodies for control. 2) The cells and beads were incubated at 4°C for 30 minutes, and placed on a magnet for cell separation. Cells positive for either MOC31 or BM-7 were retained by the magnet while the negative cells were decanted off into separate tubes. 3) All cell fractions were subjected to individual RNA isolation and RT-PCR analysis. One patient sample could thus yield a maximum of five different cell fractions for RT-PCR. IMS positive fractions were analyzed for three PCR targets while the much larger negative fractions were analyzed using five targets.