The idea for this volume was conceived during a discussion in the hallway at a conference in early 1990. "What is the best way to detect and define pluripotent hematopoietic stem cells?" was the question posed by Dr. Fritz Melchers. After discussing the pros and cons of the available assays for quite some time, it became apparent that this topic required a wider expertise and merited a larger forum. Thus, we decided to extend the discussion and to compile the results in this volume. Much to our delight. many of the pioneers of recent experimental and theoretical developments in stem cell research agreed to contribute their expertise to answer the question. These authors review both past findings and present insights, thus providing an overview of the evolution that has been and is occurring in the field of stem cell research. In the light of recent trailblazing developments in both experimental models and in clinical application it is indeed time to reevaluate our knowledge about stem cells. Trans plantation of hematopoietic stem cells has become more and more prevalent as a curative therapy in a variety of acquired and genetic diseases, including cancer, radiation accident, as an agent for gene therapy, and perhaps even as treatment for autoimmune diseases. Stem cells are now derived not only from bone marrow but also from peripheral blood, cord blood, and fetal liver, greatly increasing their availability for human transplantation and in some cases (fetal tissues) obliterating the need to match donors and hosts.

It is remarkable that each month the quantity ofarticles published on AIDS still that address numbers in the thousands. The basic, clinical and sociological aspects this epidemic have been vigorously investigated, and equally as extensively reported in traditional as well as new journals. Therefore, what can the reader ofthis volume expect to find that is different from the information already found in the literature? The authors of this text met in October 1993 to discuss not only AIDS and its effects on the nervous system but also to address the problem from the point of view of the diverse technologies that are used in understanding the disease. Just as the recog nition ofoncogenic viruses gave us insights into cellular genes that govern growth, the study ofHIV-I in the nervous system has opened new areas ofinvestigation in the nervous system. Use of human fetal and glioma-derived cell cultures, discovery of toxins in the nervous system, release and damage of cytokines in the brain, the neuropathic effects of HIV proteins, the investigation of new treatment for neuro AIDS, and virus detection strategies to identify latent HIVI infection are described in this volume. Basic and clinical investigators from more than thirty laboratories around the world contributed to the ideas discussed at the meeting, "Technical Advances in AIDS Research in the Human Nervous System.

Immunology has come a long way in the hundred or so years since the general concepts were first enuciated by Metchnikoff, Ehrlich, Von Bebring and others, One of the landmarks in this progress was the invention and development of monoclonal antibody secreting hybridomas by Milstein and bis co-workers in Cambridge. Unlike most modern inventions of this importance that of monoclonal antibody production was made available to the scientific community tbroughout the world unimpeded by patent protection. This may explain tbe unusual rapidity witb which it has been applied to the benefit of mankind in general. This book, representing as it does the proceedings of tbe first International Symposium to be held on the clinical appli cations of monoclonal antibodies, shows just how much bas been achieved within the space of little more than a decade. The enormaus promise of monoclonal antibody technology, which became apparent soon after its discovery, has already progressed a long way towards fulfillment. The contributors to tbis volume, all of whom are actively engaged in monoclonal antibody development and application, represent the state of the art. Professor Vincent Marks V INTRODUCTION It has been some twelve years since the pioneering experiments of Köhler and Milstein led to the discovery of monoclonal antibodies. Single molecular species antiborlies with desired specificities could be produced by the fusion of antibody - producing cells with neoplastic cells.