Microenvironments in Haemopoietic and Lymphoid Differentiation. Ciba Foundation Symposium 84

One of the central questions in cell biology is what mechanisms govern the proliferation and differentiation of cells. Understanding the factors that control a stem cell's decision to divide and/or differentiate is a formidable task which would have great implications across biology and medicine. In addition to holding the key to the pathogenesis of numerous diseases, comprehending these factors would enable us to approach the ultimate example of differentiation, the growth of a single-cell zygote into a mature organism. In order to begin to study differentiation, it is necessary to have a good system in which to work. Among the many cell types employed, the hemopoietic and lym-phoid lineages have frequently been used because of their easy maintenance in culture, their clearly observable morphological and functional changes, and their numerous analogues in clinical medicine. This volume, the proceedings of a symposium held in London in November 1980, explores the environmental factors (cellular, matrix, and soluble) which influence differentiation in these cells. The first half of the book deals with hemopoiesis. Systems of bone marrow cultures are described which structurally resemble normal bone marrow, and produce cells differentiating along all of the hemopoietic pathways. One striking example of the importance of environment in differentiation is an experiment described by T.M. Dexter. He used two genetically anemic strains of mice, both of which showed defective hemopoiesis in vitro. It was shown that one had defective stem cells, while the other had defective stromal cells; the normal stromal cells from the first strain were able to complement the normal stem cells of the second to give normal hemopoiesis in vitro. These studies of bone marrow cultures may greatly aid the understanding of hemopoiesis in vivo, and correlates in clinical medicine are discussed. The second half of the volume deals largely with how cells committed to lymphoid development acquire their antigen specificity. This includes the role of the thymus and histocompatability antigens in T cell maturation, B cell differentiation in ger-minal centers, and the physiology and interactions of antigen presenting cells. The papers in this section straddle the line between lymphoid differentiation and im-munology, though, in addition to their inherent interest, they reinforce the importance of soluble factors, matrix, and contact with other cells in cellular differentiation. As in the papers of the first half, widespread use is made of monoclonal an-tibodies to correlate anatomical localization of cells with their surface antigen expression , …