[Effect of streptolysin "O" on cell division and sister chromatid exchange]

The changes of mitotic activity and sister chromatid exchanged (SCE) of cultured human lymphocytes under the effect of streptolysin "O" have been studied. Lymphocyte cultures from 9 normal donors were treated with 4 concentrations of streptolysin "O" (0.05, 0.1 0.2 and 0.3 E/ml). Mitotic index in culture (33 100 cells were observed) decreased in inverse proportion to a dose of streptolysin "O" (p = 0.001). Analysis of 455 metaphases (102 control samples and 353 treated with the toxin) showed that streptolysin "O" induced significant increase in the frequency of SCE in cells and in chromosomes (p = 0.001). The frequency of SCE was highest at the lowest dose of toxin (0.05 E/ml) and decreased gradually according to the raising concentrations of toxin in cultures (p = 0.001). The data obtained permit to conclude that streptolysin "O" in concentrations used induces sister chromatid exchanges as well as inhibits mitotic activity in human lymphocytes in vitro.