Migration of small lymphocytes in adult mice demonstrated by parabiosis

Human bone marrow lymphocytes. Cytotoxic effector cells in the bone marrow of normal individuals

This study was undertaken to determine the capability of lymphocytes in the bone marrow of normal individuals to mediate nonspecific killer cell functions in assays of phytohemagglutinin (PHA)-induced cellular cytotoxicity, and antibody-dependent cellular cytotoxicity (ADCC) against 51Cr-labeled chicken erythrocyte target cells. Relatively pure mononuclear cell suspensions were obtained from bone marrow aspirates in 30 normal volunteers by sucrose gradient centrifugations and from the peripheral blood of the same individuals by Hypaque-Ficoll density centrifugations. At an effector: target ratio of 10:1, the PHA-induced cellular cytotoxicity of peripheral blood was 78.8 +/- 1.3%, while that of bone marrow was not significantly less at 66 +/- 9% (P greater than 0.1). At low effector:target ratios, the ADCC of bone marrow was negligible, while at higher effector:target ratios (20:1) bone marrow ADCC was 69 +/- 3.7%, which was comparable to that of peripheral blood. The lymphocytes themselves in the mononuclear cell suspensions of both peripheral blood and bone marrow were capable of cytotoxicity activity since depletion of monocytes from the suspensions by adherence to rayon wool and G-10 Sephadex columns did not remove the cytotoxic activity. Blocking of the Fc receptor on the effector cells by the addition of aggregated gamma globulin to the cultures suppressed the ADCC but not the PHA-induced cellular cytotoxicity of both peripheral blood and bone marrow, indicating that ADCC is dependent on an Fc receptor on the effector cell in both compartments. These studies demonstrate that the bone marrow of normal humans contains populations of lymphoid cells which have highly efficient killer cell capacities. It is uncertain what portion of these cells arise in the bone marrow and what portion enter the bone marrow parenchyma as part of the recirculating lymphocyte pool. These findings have relevance in the clearer understanding of the killer cell potential of grafted human marrow, as well as the bone marrow sequestration of functionally capable lymphocyte subpopulations in disease states and during chemotherapy.

Human bone marrow lymphocytes. I. Distribution of lymphocyte subpopulations in the bone marrow of normal individuals

This study was undertaken to determine the proportions and in vitro immune capacities of lymphocyte populations in the bone marrows of normal humans. Relatively pure mononuclear cell suspensions were obtained from bone marrow aspirates by linear sucrose gradient centrifugations. Simultaneous peripheral blood and bone marrow specimens from each individual were assayed for lymphocyte surface markers and mitogen responsiveness. Maximal possible contamination of bone marrow aspirates by peripheral blood was determined by performing aspirates on individuals who had received 51chromium-labeled autologous erythrocytes. Rhymus-derived (T) lymphocytes, as determined by the sheep red blood cell (E) rosette assay, comprised 8.6-(plus or minus 1.6)% of the total bone marrow lymphocyte pool. Bone marrow-derived (B) lymphocytes, as determined by the presence of a complement receptor, made up 15.4-(plus or minus 1.9)% of the lymphocyte pool whereas 74.6 (plus or minus 2.4)% of mononuclear cells lacked easily detectable surface markers. These findings could not be explained by contamination with peripheral blood lymphocytes since contamination was corrected for in the calculations. Lymphocyte-enriched suspensions of bone marrow cells responded to stimulation with phytohemagglutinin, concanalin A, and particularly pokeweed mitogen. In vitro incubations of bone marrow and peripheral blood lymphocytes with tritiated thymidine followed by determinations of E and erythrocyte antibody complement (EAC) rosettes were performed. Simultaneous rosetteradioautographs demonstrated that the proliferative potential of bone marrow B lymphocytes was greater than peripheral blood B lymphocytes (P less than 0.01). On the other hand, the proliferative potential of bone marrow T lymphocytes was the same as that of peripheral blood T lymphocytes. These findings demonstrate that in addition to containing B lymphocytes the normal bone marrow contains a small fraction of T lymphocytes similar to the mature T lymphocyte pool found in the peripheral blood. These T cells most probably enter the bone marrow parenchyma as part of the normal recirculating lymphocyte pool.

Alternate-day prednisone therapy and human lymphocyte subpopulations

The mechanisms and kinetics of the immunosuppressive effects of alternate-day prednisone were investigated in a group of patients with a variety of inflammatory diseases receiving a range of alternate-day prednisone doses from 5 to 120 mg. Total circulating lymphocyte and monocyte counts, as well as proportions of lymphocyte subpopulations defined both by surface markers and by in vitro functional capacities, were studied. At 8 a. m. of the day on prednisone, just before drug administration, lymphocyte and monocyte counts, proportions of lymphocyte subpopulations, as well as in vitro lymphocyte blastogenic responses to various mitogenic and antigenic stimuli were normal. 4 h after the administration of prednisone, there was a profound lymphocytopenia and monocytopenia, with a differential depletion of thymus-derived lymphocytes as well as various functionally defined lymphocyte subpopulations. Lymphocyte kinetic studies using a radioactive chromium-labeled autologous lymphocytes showed that the lymphocytopenia was due predominantly to a transient depletion of the recirculating portion of the intravascular lymphocytepool. All these parameters returned to normal by 8 a.m. of the following day (off prednisone) and remained normal throughout the day. This very transient lymphocytopenia and monocytopenia after prednisone, with normal cell numbers, proportions, and functions throughout the remainder of the 2-day cycle, was associated with suppression of disease activity, yet did not affect cutaneous delayed hypersensitivity in these patients nor increase the likelihood of infectious complications. This drug-associated cyclic and transient monocytopenia and selective lymphocytopenia is best explained by a redistribution of recirculating lymphocytes to other body compartments, particularly the bone marrow.