International Journal of Cell Cloning, Vol 10, 144-152, Copyright © 1992 by AlphaMed Press
Novel factors from stromal cells: bone marrow and thymus microenvironments
JD Watson and HJ McKenna
Department of Molecular Medicine, University of Auckland, New Zealand.
The microenvironments contained within mammalian bone marrow and thymus
play major roles in the life-long process of myeloid and lymphoid cell
development and renewal. The cells that give architecture to these
microenvironments are collectively referred to as stromal cells, and these
cells grow as adherent cell types in cell culture. Stromal cells are
predominantly a mixture of fibroblasts, cells of macrophage/dendritic
lineages, epithelial and endothelial cells. There are at least three
mechanisms that govern the interaction of stromal cells with hematopoietic
and lymphoid cells: soluble factors, or cytokines, membrane-anchored growth
factors and cell surface recognition molecules, such as integrins and
selections. Little is known of the mechanisms that preserve the integrity
of local microenvironments and how subpopulations of cells are transiently
retained in microenvironments during various maturational states. Different
lymphoid cells develop in bone marrow and thymus despite the similarities
in stromal cells of these tissues. It remains a major quest to determine
how the components of microenvironments of these organs regulate
lineage-specific differentiation. The focus here is on stromal cells, the
early development of myeloid cells and B lymphocytes in bone marrow and T
lymphocytes in the thymus.
