Reappraisal of karyological monitoring of diploid cell substrates.

The practical aspects of present requirements for karyological monitoring of diploid human fibroblasts used in vaccine production are critically re-examined. A brief review of known chromosomal instabilities and their correlations with neoplasia and with in vitro conversions of cell growth is presented and discussed in relation to karyological criteria in the selection of mammalian diploid cell substrates. It is proposed that extensive experience with the growth and karyological characteristics of human diploid fibroblast cell strains of embryonic origin may warrant the reduction or elimination of karyological monitoring of production lots. Additional requirements for characterization of cell strains for approval as substrates for vaccines are suggested which involve evaluations of chromosomal stability based upon (a) viral transformation rate and (b) aberration production rate in response to x-irradiation.