Induction of Ly-49 on an Interspecies Hybridoma between Differentiation Stage Specific Murine T Cells and a Rat T Lymphoma

Ly-49 can be expressed in interspecies hybridoma cells resulting from the fusion of Ly-49 negative lymphoid cells from normal mice and Ly-49 negative T cells from the rat thymoma W/ Fu(C58NT)D (C58). Several hundred hybridoma clones of this type were studied. Hybridoma clones derived from the fusion between activated C57BL/6 mouse spleen cells and C58 expressed Ly-49 on their surface although Ly-49 was undetectable on both parental cells. No Ly-49 antigen was expressed on hybrids when BW5147, a T lymphoma derived from AKR mouse, replaced C58 as parental cell. Thymocytes from C57BL/6 mice also produced Ly-49 positive interspecies hybridomas with C58. Subsequent manipulation of these thymocytes with a mixture of anti-CD4 and anti-CD8 antibodies plus complement to obtain double negative cells (CD4-/CD8-) prior to the fusion abolished the expression of Ly-49 on hybridomas. On the other hand, if the thymocytes were treated with either anti-CD4 or anti-CD8 antibody plus complement, the resultant thymocytes which were a mixture of cells with a single positive (CD4+/CD8- or CD4-/CD8+) and a double negative phenotype (CD4-/CD8-) retained the ability to produce Ly-49 positive hybridomas. Interspecies hybridomas between either CD4+/CD8- or CD4-/CD8+ functional T cell clones and C58 expressed Ly-49 on their surface, though these parental T cells lacked Ly-49 on their surfaces. Northern hybridization analysis using Ly-49 cDNA revealed that C58 cells do not express Ly-49 mRNA, indicating that a trans-acting factor(s) from C58 plays an important role in the induction of cell surface Ly-49 expression on interspecies hybridomas. Our data indicate the complex nature of the regulatory mechanisms for expression of the Ly-49 molecule.