Spontaneous sister-chromatid exchange frequencies in human B and T lymphocytes at BrdU borderline concentrations for sister-chromatid differentiation.

Human peripheral blood B and T lymphocytes, highly purified by immunologic methods, were supplemented with gamma-irradiated unseparated autologous mononuclear cells to restore helper functions and stimulated with pokeweed mitogen and phytohemagglutinin, respectively. Spontaneous sister-chromatid exchange (SCE) frequencies were investigated in proliferating B and T lymphocyte cultures labeled with the cell-type-specific borderline concentrations of 5-bromodeoxyuridine (BrdU) for sister-chromatid differentiation (SCD). B lymphocytes from 6 different donors showed mean values of 3.28-3.72 SCE events/cell. In T lymphocytes, mean values of 6.30-7.28 SCEs/cell were observed. The differences between the SCE distributions of the cell populations are highly significant. The results show that the differences in the spontaneous SCE frequencies between human B and T lymphocytes were not due to a difference in the uptake of BrdU.