Interaction of antibody and cell surface localized antigen

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.

Shedding of anti-IgM from antibody-coated human lymphoma lines: differences between Epstein-Barr virus-negative lines and their virus-converted sublines

In vitro converted, Epstein-Barr (EBV) genome-carrying cell lines showed a reduced ability to shed surface-bound antibodies, compared to their EBV-free parental B lymphoma lines. On the other hand, antibody degradation was higher with EBV-positive cells. Analysis of antibody-coated single cells revealed that cells which failed to redistribute or cap their ligand-bound surface components at 37 degrees C, were also capable of shedding bound antibody. This suggests that capping and shedding are essentially independent phenomena, although both may be influenced by the same virally induced change in the lateral mobility of membrane constituents.

Antibody-induced antigen redistribution and shedding from human breast cancer cells

Cell surface antigens of human breast cancer cells undergo a rapid redistribution when bound by antibodies from cancer patients. The subsequent shedding of these antigen-antibody complexes and free antigen may be instrumental in tumor survival.