The interaction between bone marrow immune suppression and hematopoiesis

Murine bone marrow is known to contain a suppressor cell that suppresses in vitro immune responses, although its in vivo role is unknown. This cell was found to be lacking standard lymphocyte markers, including Thy 1, Lyt 1, Lyt 2, Fc receptors, and surface immunoglobin. A second cell, which acts to mask the activity of the bone marrow suppressor, was detected in neonatal mice. In the presence of this modifying cell, which was Thy 1+, the net amount of marrow suppression was decreased. A similar, though smaller, decrease in suppression could also be induced by making adult mice anemic through periodic bleeding. The parallel changes of hematopoiesis and marrow suppression suggest that these functions of the marrow are functionally linked, possibly via the Thy 1+ suppression-modifying cell.