and how the known vertebrate homologues of these genes are expressed normally in differentiation and proliferation pathways as well as abnormal ly in well-defined lymphomagenic and other oncogenic pathways. What emerged from this meeting are a better understanding of the evolution of these gene systems themselves and an elucidation of simpler systems open to more rapid genetic and molecular genetic analysis to reveal the normal functions of these genes and their gene products. Thus we sought new answers to several old questions concerning differenti ation, proliferation, and neoplastic transformation. We gathered together in an unusual format - that of the unique Dahlem Workshops - not just to reiterate data which has recently emerged but to think about how these findings might lead to new approaches for the understanding and therapy of the leukemias and lymphomas. We deliberately chose experts from several different disciplines, ranging from the clinicians who diag nose, describe, and treat these maladies, to the molecular geneticists trying to reduce the analysis of the problem to its simplest variables in the simplest systems possible.

Inhalt
Specificity of Hemopoietic Growth Factors.- T Cell Proliferation and Differentiation.- Regulatory Defects in Leukemia: In Vitro Analysis.- Induction of B Cell Proliferation and Differentiation.- Lymphoid Tumor Stem Cells and Their Regulation.- Phenotypic Heterogeneity and the Origins of Lymphoid Malignancy in Man: Biological and Clinical Implications.- Differentiation of T Lymphocytes.- Effects of Acute Leukemia Viruses on the Differentiation of Hematopoietic Cells.- Multiple Mechanisms of Oncogene Activation in Viral and Nonviral Neoplasia.- Oncogenes of Avian Leukemia Viruses.- Significance of Chromosome Rearrangements in Leukemia and Lymphoma.- Tracing Development and Cell Lineages in Human Hemopoietic Neoplasia.- The Preleukemic State in Virus-induced Leukemia.- The Receptor-mediated Leukemogenesis Hypothesis: A Model of Retroviral Oncogenesis by Viral Stimulation of Cell-surface Receptors.- Regulation of Hematopoietic Differentiation and Its Disruption.- Group Report.- Problems in Differentiation Pathways and Cellular Targets for Leukemogens.- Group Report.- Genes and Viruses Able to Transform Hematopoietic Cells.- Group Report.- Evolution of the Leukemic State.- Group Report.- List of Participants with Fields of Research.- Author Index.