Animal cell technology is a growing discipline of cell biology which aims to understand the structure, function and behaviour of differentiated animal cells, and especially the development of such abilities as are useful for industrial purposes. These developments range from clonal expansion of differentiated cells with useful abilities, to optimization of cell culture on an industrial scale and modulation of the cells' abilities to produce drugs and monoclonal antibodies. The sixth volume in this series gives a review of today's state of the art in Japan, a country where this field is especially well advanced. It should be of interest to cell biologists, biochemists, molecular biologists, immunologists and other disciplines related to animal cell culture, working in the academic environment as well as in the biotechnology or pharmaceutical industry.