A CHARACTERIZATION OF T-LYMPHOCYTE COLONY-FORMING CELLS (TL-CFC) IN HUMAN-BONE MARROW

Abstract

T lymphocyte colony-forming cells (TL-CFC) present in the peripheral blood of healthy [human] individuals have been studied, but an analysis of the properties of marrow TL-CFC is still lacking. A 1st attempt to define some characteristics of marrow TL-CFC and blood TL-CFC have different density properties. Both populations were characterized by distinct profiles with peaks at 1.071 g/ml and 1.065 g/ml, respectively. In marrow and blood, striking similarities between the density distributions of TL-CFC and E [erythrocyte] rosette-forming cells (E-RFC) were found. From E rosette Ficoll separation experiments it became clear that TL-CFC in bone marrow and in blood represent a subgroup of the E-RFC population. A marked dissociation was observed between the quantitative values of thymidine incorporation and colony responses following stimulation with PHA [phytohemagglutinin]. Light-dense bone marrow subfractions, which were virtually negative in PHA mitogen (DNA-synthesis) tests, still gave rise to relatively large numbers of T lymphocyte colonies after stimulation with PHA. In blood, T lymphocyte colonies could be grown exclusively from density fractions which were positive in PHA mitogen stimulation tests. Apparently, characteristic differences exist between marrow and blood TL-CFC.