Some characteristics of the cytotoxic material in human dental plaque extracts

Cytotoxic activity of dental plaque can be extracted into saline and assayed by its inhibitory effect on the growth of HeLa cells. The toxic activity was determined after fractionating the plaque extracts by dialysis into distilled water and by filtration through Diaflo membranes and Sephadex gels. More than 50 per cent of the toxic activity was non-diffusible and inactivated by heating. This material was possibly a self-aggregating protein which had a monomeric molecular weight of 30,000. The remainder of the toxic activity was diffusible, was stable to heating and had a molecular weight of about 225.