Survivors 
4/8 
7/8 
Figure 2. Diameter of MCA 106 tumor after injection with the 
indicated vectors and survival after intratumor injection of H- 
2K S or /9-galactosidase. 
XI. Mechanism of tumor cell cytolysis. 
Previous studies did not show whether the cytolytic response 
to the foreign MHC gene transduced cells or to autologous tumor 
cell antigens is mediated by T cells or other cell types. To 
address this question, we have performed cytolytic T cell assays 
in the presence or absence of anti-Lyt2, using an antibody to 
LT34 (of the helper T cell subset) as a negative control. In all 
cases, cytolysis was substantially reduced by the anti-Lyt2 
antibody, both in instances where animals were pre-immunized with 
H— 2K S or in the absence of pre-immunization to H-2K S . It should 
also be noted that the pre-immunization in this model system is 
successful if made against the recombinant gene that will be 
introduced. For example, C57BL/6 mice pre-immunized with CT26 K s 
cells are able to reject MCA 106 cells injected with H-2K S 
vector. Therefore, it is not necessary to pre-immunize with the 
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Recombinant DNA Research, Volume 15 
