Karyotypic analysis of murine cytolytic T-cell lines

G-banding techniques have been used to analyze the karyotypes of four independently derived murine cytolytic T lymphocyte (CTL) lines established in culture 2-4 yr earlier. For two of them, several subclones were included in the analysis. The modal arm number of three of the lines was close to diploid, whereas in the fourth line, both near-diploid and near-tetraploid subclones were found. The most frequent type of rearrangement was the formation of metacentrics by centromeric fusion. A comparison of the abnormalities (markers) occurring in the different CTL lines showed the formation of similar chromosomal rearrangements in independent lines, thus suggesting nonrandom chromosomal changes in these cells. Several of the metacentrics are derived from the fusion of normal murine chromosomes that are apparently prone to form such "markers," as the occurrence of similar abnormalities has been reported in other established cell lines and tumors. On the other hand, some of the biarmed and telocentric marker chromosomes seem to characteristically occur in CTL but not in other types of cell lines.