In vivo detection of fluorescent tumor-specific cytotoxic T cell clones

Cytotoxic T lymphocytes (CTL) can be very effective mediators of tumor-specific immunity in vivo. Since little is known about the in vivo behaviour of cultured tumor-specific CTL, a fast and simple method has been developed utilizing a lipophilic carbocyanine, 1,1'-dioctadecyl 3,3,3',3'-tetramethylin-docarbocyanine perchlorate (DiI), for the in vivo detection of tumor-specific CTL clones in (tumor-bearing) mice. The two CTL clones used in this study are directed against human papillomavirus type 16- or human adenovirus type 5 early region 1 (Ad5E1)-transformed mouse embryo cells. Growth ability, cytotoxic capacity and tumor-eradicating potential remained unaltered when the CTL were labeled with this dye. Thus, in neither in vitro nor in vivo testing was the biological function of the CTL clones affected. The in vivo localization in the spleen of an adoptively transferred DiI-labeled Ad5E1-specific CTL clone is described. This adoptively transferred CTL clone was also detectable at the site of a subcutaneously growing human Ad5E1-induced tumor within 1 day after intravenous injection.