HOMING OF BONE MARROW LYMPHOID CELLS

Abstract

SUMMARY DNA labeling, bone marrow fractionation, and radioautography were used to follow the fate of transfused, newly formed marrow lymphocytes in irradiated hosts. After infusing donor Hartley guinea pigs with ³H-thymidine for 3 to 5 days, high concentrations of labeled small lymphocytes and large lymphoid cells were separated from marrow by sedimentation in sucrose-serum gradients and injected into lethally X-irradiated syngeneic recipients. Most labeled small lymphocytes and large lymphoid cells rapidly left the circulation. They appeared to be mainly in the marrow and spleen, increasing in incidence from 1 to 3 days, but declining in mean grain count. Labeled cells were scattered throughout the recipient marrow; in the spleen they localized initially in the red pulp, and subsequently in peripheral areas of white pulp, often in clusters. Labeled small lymphocytes showed a delayed migration into the mesenteric lymph node, mainly in the superficial cortex and medulla; they also appeared in small numbers in Peyer's patches, but rarely in the thymus or thoracic duct lymph. It is concluded that a rapid selective homing of newly formed marrow lymphoid cells occurs in both the marrow and certain areas of the spleen of irradiated hosts, followed by a continuing proliferation of large lymphoid cells and production of small lymphocytes. The results are discussed with respect to the life history of marrow lymphocytes and the use of adoptive immune assays of marrow cells to characterize B lymphocyte maturation.