Studies of cellular immunotherapy in cancer patients have evaluated two effector 
populations. Lymphokine activated- killer (LAK) cells, generated by short term 
culture of peripheral blood lymphocytes in the presence of high concentrations of IL2, 
lyse transformed target cells and have minimal lytic activity for most normal tissues 
[33,34]. Up to 10 n in vitro generated LAK cells have been administered in a single 
intravenous infusion to cancer patients. Treated patients experienced only minor 
constitutional symptoms and no pulmonary compromise demonstrating the safety of 
systemically administering large numbers of in vitro activated lymphocytes [35-37]. 
Therapeutic trials have also combined short courses of high dose systemic IL2 
administration with LAK cell transfer to promote LAK function and viability with 
apparent enhanced efficacy. 
Therapy with in vitro expanded lymphocytes derived from a tumor infiltrate has also 
been evaluated. The rationale for using such tumor infiltrating lymphocytes (TIL) is 
that these lymphocytes might be enriched for tumor-reactive T cells, and such TIL 
cells have been shown in a murine sarcoma model to be 50 to 100 times more 
effective than LAK cells in eradicating tumor micrometastasis [38]. In humans, TIL 
cells lines have been generated by mincing tumor specimens and culturing eluted 
lymphocytes with high concentrations of IL2. TIL lines can be expanded to 10 8 -10“ 
cells over 3-8 weeks in culture, and some lines appear to function as T cells with lytic 
specificity for autologous but not allogeneic tumor targets, whereas others function as 
LAK cells and lyse both autologous and allogeneic tumor targets [39-41]. Adoptive 
transfer of 5xl0 10 TIL alone has not been associated with significant toxicity, and 
administration of 5xl0 10 TIL cells with concurrent systemic IL2 has resulted in 
toxicities that are attributable to the IL2 [42,43]. Evaluation of the migration patterns 
of transferred TIL cells by infusion of Indium-111 labelled cells has revealed initial 
localization of TIL cells in the lungs, liver and spleen at two hours after intravenous 
infusion, followed by emigration and preferential localization at sights of metastatic 
tumor by 24 hours [44]. Partial and complete tumor regressions have been seen in 
patients following a single TIL cell infusion, demonstrating these long term cultured 
immune effector cells can mediate in vivo biologic effects. 
2. Infusion of lymphocytes modified by retrovirus mediated gene transfer 
The use of replication-defective retroviral vectors has advanced gene transfer 
technology resulting in clinical applications. These vectors can be produced free of 
helper virus using specially designed packaging cell lines such as PA317 and provide 
a suitable means of transducing primary T lymphocytes. The retroviral marker can be 
used in combination with polymerase chain reaction (PCR) techniques to allow the 
transduced cells to be tracked in vivo following cell transfer, and genes inserted into 
these vectors may be expressed by placing them under appropriate transcriptional 
control. Recently, TIL from several different individuals have been transduced with a 
retroviral vector expressing the neomycin phosphotransferase gene which confers 
resistance to toxic doses of G418 [46]. These TIL have been administered to cancer 
patients and the presence of the marker gene encoding neomycin phosphotransferase 
used to determine the in vivo persistence and distribution of transferred T cells. 
Preliminary results from these studies have demonstrated the localization of TIL cells 
at tumor sites long after cell transfer and illustrate the feasibility and safety of using 
retrovirus mediated gene transfer to mark human T cells to be used for 
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