T cell function detected in murine bone marrow cells.

Mouse bone marrow cells were fractionated by BSA discontinuous density gradient centrifugation, and a small lymphocyte rich fraction was obtained at the high density. Cells of this fraction were shown to respond in vitro to T cell mitogens and alloantigens. Furthermore, they were able to mount a graft-versus-host reaction when assessed by spleen weight assay and by the method of inhibiting erythroid cell growth by allogeneic lymphoid cells. The results indicate that these lymphocytes possess T cell functions. On the other hand they were found to carry only little theta antigen assessed by the cytotoxic test and by the absorption test. It is presumed, therefore, that the amount of theta antigen on a cell might not correlate with T cell functions, and these lymphocytes might be mature ones in the course of postthymic maturation. Hemopoietic stem cells were determined by spleen colony formation and the peak of colony-forming efficiency was seen at the low density. These observations imply that immunocompetent cells causing GVHR can be separated from hemopoietic stem cells. This procedure may be applied for prevention and reduction of GVHR in allogeneic bone marrow transplantation in human.