Molecular interactions between stromal cells and B lymphocyte precursors.

Long term culture techniques, cloned stromal lines, recombinant cytokines and monoclonal antibodies have provided powerful experimental tools for studying bone marrow functions. Rapid progress has been made in characterizing large reticular stromal cells in bone marrow that provide a nurturing microenvironment for B lymphocyte precursors. It is now clear that they have differentiation potential, that they can respond to inflammatory episodes and that they can make at least 12 regulatory cytokines. Pairs of cell adhesion molecules have also been defined which participate in B lymphopoiesis. These include CD44, hyaluronate, VLA-4 and a VCAM-like protein.