Chapter 6 Control of Membrane Fusion in Polyethylene Glycol-Resistant Cell Mutants Applications to Fusion Technology David S. Roos, Richard L. Davidson, and Purnell W. Choppin 1. INTRODUCTION AND OVERVIEW Cell fusion has been studied for more than a century (Langerhans, 1868) as a curious morphological phenomenon, occurring in certain developing tissues (Kalderon, 1980) and during the progression of a variety of tumors and viral infections (Roizman, 1962; Guccion and Enzinger, 1972). Only with the use of cell hybrids in somatic cell genetics, however, did the im- petus arise to develop fusion technology as an applied art, placing a pre- mium on the control of cell fusion (Davidson, 1977). The development of procedures for hybridoma production has made cell fusion a fundamen- tal tool of the growing biotechnology industry (Kohler and Milstein, 1975), and it is not surprising that improvements in the efficiency of cell hy- DAVID S. Roos • Department of Biology, Stanford University, Stanford, California 94305. RICHARD L. DAVIDSON • Center for Genetics, University of Illinois, Chicago, Illinois 60612. PURNELL W. CHOPPIN • Virology Laboratory, Rockefeller University, New York, New York 10021. Present address: Howard Hughes Medical Institute, Bethesda, Maryland 20814. 123 A. E. Sowers (ed.), Cell Fusion © Springer Science+Business Media New York 1987