Clonotypic chromosomal aberrations in long-term lines of myelin-specific rat T lymphocytes

A panel of 16 long-term rat T lymphocyte lines and clones were screened for cytogenetical abnormalities using chromosomal banding techniques. All T lines were CD4+, recognizing the relevant antigen in the molecular context of major histocompatibility complex (MHC) class II determinants. With one exception (an ovalbumin-specific line), all lines were specific for myelin proteins, and apart of one BS rat-derived T line and its clones, all lines were selected from the Lewis strain of rat. After in vitro culture of more than 1 year, all lines and clones exhibited subtle but definite chromosomal aberrations, which included deletions, enlargement, translocations and formation of isochromosomes. All lines were near diploid, structural chromosomal changes being more frequent than numerical abnormalities. Each T line investigated had an individual pattern of chromosomal changes. In our analysis, 16 of the 22 different chromosomes had changes in at least one line. Chromosome 9 and the X chromosome appeared to have an enhanced susceptibility of alterations. In two cases, chromosomal markers could be traced through different stages of in vitro culture of the T lines.