Electric field-induced cell-to-cell fusion

Cell-to-cell fusion has great potential in membrane research, membrane reconstitution and genetic mapping [25, 34, 49]. Furthermore, both somatic hybridization and genetic engineering offer a way of modifying plant cells and, in turn, of improving crops [49, 53]. If lymphocyte cells are fused with a permanent cell line so-called hybridoma cells are produced [32] which are capable of producing monoclonal antibodies of predetermined antigenic specificity. These hybridoma cells (antibody-producing hybrids) can be envisaged as important tools in future clinical diagnosis and therapy as well as in the purification and enrichment of compounds of cell-biological and medical interest [18, 65, 72]. However, despite many promising results and considerable efforts, fusion still seems to be something of an art rather than a precise science. Phenomenologically, cell-to-cell fusion is achieved presently in vitro by chemicals or inactivated virus [2, 30, 31, 33, 34, 48, 64]. Fusion can usually only be achieved by using membrane-disrupting agents and procedures and/or unphysiological conditions (e.g., high Ca/+ concentrations, high or low pH values, hypotonic conditions, etc.) The field of chemically and virus-induced fusion has been excellently reviewed by several authors over the last years [17, 34, 45, 47, 48]. In view of the bewildering array of data on chemically and virusinduced fusion we are obliged to conclude that we are still far from solving the molecular mechanism underlying the fusion process. Any progress in this field and in the development of novel fusion techniques will have to be evaluated by comparison with the inherent limitations of the current fusion procedures, which are listed below: