vivo was assessed using a standard 51 Cr release assay. Cytolytic 
T cells were present in spleens of animals which received 
intratumor injection without prior immunization to H-2K S but not 
/3-galactosidase using vector II (Fig. 4) . These results indicate 
that systemic immunity against tumor cell antigens has been 
obtained and that the RSV enhancer was functional. In addition, 
in the CT26 tumor, we inoculated 10 6 cells on the side 
contralateral to tumors injected with H-2K S . The side opposite 
to the treated tumor failed to grow in such animals, suggesting 
that systemic immunity can be achieved against 51 Cr-labeled using 
this anti-tumor protocol. 
EFFECT ORrTARGET RATIO 
<%> 
Figure 4. Cytolytic T cell activity in CT26 tumor-bearing 
animals injected with RSV expression vectors. Spleen T cells 
were derived as described previously from animals treated with 
the indicated vector and tested against CT26 or CT26K S cells. 
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Recombinant DNA Research, Volume 15 
