Abstract

Bone marrow lymphocytes were studied on twenty healthy adults. Bone marrow lymphocytes were fractionated by BSA density gradient centrifuge. The population of bone marrow lymphocytes averaged as follows; E-RFC 8.9%, thymocyte-antigen positive cells 0.4%, Tγ 0.4%, Tμ 1.4%, SmIg⁺ cells 7.8%, EAC-RFC 11.7%, EA-RFC 6.2%, and K cells 2.8% respectively. About 80% of bone marrow lymphocytes were null lymphocytes. Bone marrow null lymphocytes were intermediate in size between small lymphocytes and lymphoblasts. Their nucleus contained no nucleolus and was leptochromatic. A lot of micro-villi was demonstrated on their surface membrane and their cytoplasma contained a few ribosomes and central dense bodies.
When bone marrow null cells were mixed lymphocyte cultured with allogeneic normal T lymphocytes and then stimulated with PWM, there appeared clg positive cells, indicating that bone marrow null cells could differentiate to the antibody producing cells under the regulation of T-cells by the antigenic stimulation.