EVIDENCE OF SURFACE-ANTIGEN DETACHMENT DURING INCUBATION OF CELLS WITH IMMUNOMAGNETIC BEADS

We have studied the attachment of immunomagnetic beads to different ce lls, with particular interest in cells that did not, as expected, appe ar to bind antibody-coated beads. Through the use of immunofluorescenc e and laser scanning confocal microscopy it was possible to demonstrat e that beads can detach significant amounts of antigen from the surfac e of cells. This results in the appearance of antigen-depleted yet via ble cells. Moreover, the detached antigen is found to be bound to bead s and is associated with fragments of cell membrane which can also car ry other (non-bead binding) cell surface proteins. After reculturing, antigen-depleted cells can recover their normal levels of surface anti gen. Our results demonstrate the existence of an immunobead-induced ce ll membrane detachment phenomenon that can lead to the removal of all of a specific surface antigen without killing the cells, as judged by both vital staining and reculturing. An important aspect of this pheno menon is that immunoidentification of immunobead-selected populations of cells will give erroneous results. This may thus be of significance for the immunobead-based cell depletion methods that are used in medi cine.