This first volume in a projected series contains the proceedings of the first of the Keio University International Symposia for Life Sciences and Medicine under the sponsorship of the Keio University Medical Science Fund. As stated in the address by the President of Keio University at the opening of the 1996 symposium, the fund of Dr. Mitsunada Sakaguchi. The Keio was established by the generous donation University International Symposia for Life Sciences and Medicine constitute one of the core activities of the fund. The objective is to contribute to the international community by developing human resources, promoting scientific knowledge, and encouraging mutual exchange. Every year, the Executive Committee of the International Symposia for Life Sciences and Medicine selects the most interesting topics for the symposium from applications received in response to a call for papers to the Keio medical community. The publication of these proceedings is intended to publicize and distribute information arising from the lively discussions of the most exciting and current issues during the symposium. Weare grateful to Dr. Mitsunada Sakaguchi, who made the symposium possible, the members of the program committee, and the office staff whose support guaran­ teed the success of the symposium. Finally, we thank Springer-Verlag, Tokyo, for their assistance in publishing this work. Akimichi Kaneko, M. D. , Ph. D.