Adhesive interactions in hemopoiesis.

Blood cells developing in the bone marrow exhibit adhesive interactions with stromal reticular cells and specialized macrophages, and with several defined components of the extracellular matrix. Receptors that are known to participate in these interactions include certain integrins, selectins, members of the immunoglobulin superfamily, and CD44, and this list may be expected to grow. Specific inhibitors of some integrins and of CD44 have been shown to disrupt hemopoiesis in vitro; thus the function of adhesive receptors appears critical to blood cell development. The capacity of such receptors to transmit signals through the plasma membrane suggests that they regulate not just the physical interactions of hemopoietic cells, but also the responses of the cells to their environment.