I explored the effect of genetic (cloning) and non-genetic (arrangement of the method and quality of culture serum) factors upon variability of the results obtained by using the "kiss of death" method for evaluation of intercellular communication in Chinese hamster cells V79-4. Cloning had neither quantitative (intraspecies communication) nor qualitative (interspecies communication) effects. Of the non-genetic factors, the time interval of application of transferred agent (thioguanine) after plating the cells and the agent concentration were investigated. These factors did not influence significantly the results. Intercellular communication was more intensive in a less rich medium containing bovine serum than in a richer medium containing foetal calf serum. On the basis of the results obtained I conclude that the higher variability of intercellular communication values determined by the "kiss of death" method is not due to an error in the experimental method used but probably reflects the real changes in these values that occur with time in cell populations.

Institutes of Medical Research Pediatric Research Institute Brno