Chromosome and cell surface marker studies in 1-propyl-1-nitrosourea-induced thymic lymphomas of the rat.

ABSTRACT

Immunological cell surface markers were studied in seven transplantable 1-propyl-1-nitrosourea-induced thymic lymphoma lines in F344 rats by reactivity to anti-Thy-1.1, anti-rat Ig (anti-Ig), and anti-rat T-cell (anti-T) sera, and by the capacity to form rosettes with guinea pig red blood cells. All the tumor lines were estimated to be sensitive to anti-Thy-1.1 but insensitive to anti-Ig serum in the presence of complement. The differences in reactivity to anti-T serum and rosette-forming capacity (RFC) allowed classification of the lines into three types. In type I, three lines were highly sensitive to anti-T serum but low in RFC, indicating that these lymphomas probably originated from relatively mature intrathymic T cells. In type II, two lines were moderately sensitive to anti-T serum and relatively high in RFC, indicating that these lymphomas derived from intrathymic T cells. In type III lymphomas, the remaining two lines were not only insensitive to anti-T serum but also low in RFC, suggesting that these lymphomas might have arisen from immature precursors of T and/or B cells. The chromosome study revealed that type I lymphomas were diploid, with slight numerical and structural variations. Type II lymphomas were pseudodiploid or hypotetraploid, with considerable variation in the number and morphology of chromosomes. Type III lymphomas had a diploid or hyperdiploid constitution, with a moderate degree of karyotypic variation. Neither consistent nor common karyotypic alterations among the seven lines were found, although the karyotypic instability seemed to be related to the immunological types of the lymphoma lines, possibly reflecting the differentiation process of the target cells involved in the malignant transformation.