INTERSPECIES SOMATIC T-CELL HYBRIDS AS BIOLOGICAL TOOLS FOR STUDYING GENE-EXPRESSION DURING T-CELL DEVELOPMENT

Interspecies somatic cell hybrids were generated by fusing the mouse t hymic lymphoma cell line, BW5147, with normal human T lymphocytes at d ifferent stages of differentiation. Thymocytes, activated peripheral T lymphocytes, or an activated T cell clone were used as human partners , respectively, in three independent fusions. Phenotype and genetic an alysis demonstrated that these hybrids preferentially segregated human chromosomes while retaining a complete mouse genetic complement, irre spective of the human partner used for fusion. A large number of T cel l differentiation antigens constitutively expressed throughout the T l ymphocyte development remained consitutively expressed in the hybrids, irrespective of the maturation stage of human partner used for fusion . In contrast, the expression of other antigens related to a specific stage of T cell development (CD2, CD8), or to an activated state of T lymphocytes (HLA-DR, CD25), was to observed in the hybrids, with no ap parent correlation with the segregation of human chromosomes other tha n, of course, the encoding chromosome. From these results we suggest t hat the developmental stage of the fusion partners strongly influences the pattern of expression by activating or silencing genes programmed to be expressed in distinct phases of T cell ontogeny.