Evidence of surface antigen detachment during incubation of cells with immunomagnetic beads

We have studied the attachment of immunomagnetic beads to different cells, with particular interest in cells that did not, as expected, appear to bind antibody-coated beads. Through the use of immunofluorescence and laser scanning confocal microscopy it was possible to demonstrate that beads can detach significant amounts of antigen from the surface of cells. This results in the appearance of antigen-depleted yet viable cells. Moreover, the detached antigen is found to be bound to beads and is associated with fragments of cell membrane which can also carry other (non-bead binding) cell surface proteins. After reculturing, antigen-depleted cells can recover their normal levels of surface antigen. Our results demonstrate the existence of an immunobead-induced cell 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 phenomenon 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 medicine.