We have investigated the anti-
tumor activity of ex vivo activated and expanded T cells which had been sensitized in vivo to one of two different syngeneic rat
glioma cell lines; D74 or RT-2. Rats were sensitized by inoculation of irradiated
tumor cells into each hind foot pad. After 10 days, the
tumor-draining lymph node (DLN) from each popliteal region was excised and prepared as a single cell
suspension.
Tumor-DLN lymphocytes were next activated overnight in RPMI-1640 medium containing 10%
fetal bovine serum (FBS), Bryostatin-1 (5 nM),
ionomycin (1 microM), and 20 U human recombinant
interleukin-2 (IL-2) per ml. Culture for seven days in RPMI-1640 supplemented with FBS and
IL-2 resulted in approximately 100-fold expansion of the lymphocyte population. Both D74- and RT-2-sensitized T cells constitutively secreted
tumor necrosis factor-alpha, and both lymphocyte populations produced comparable amounts of the
cytokine when co-cultured with either
glioma cell line. Neither D74- and RT-2-sensitized effectors constitutively secreted
gamma-interferon (gamma-IFN), but both populations produced gamma-IFN when exposed to either
glioma cell line in vitro. D74-sensitized T cells released significantly more gamma-IFN than the RT-2 DLN lymphocytes. In vitro
Chromium-release assays indicated that RT-2-sensitized T cells were more cytotoxic for RT-2 targets than for the D74 line and that D74-sensitized effectors were also more cytotoxic for RT-2 targets. To assess in vivo therapeutic efficacy, rats who had been inoculated intradermally with RT-2 cells three days earlier received an
intravenous injection of RT-2- or D74-sensitized DLN cells (10(6) cells/gram
body weight) expanded after activation with Bryostatin-1 and
ionomycin or an equal number of lymphokine-activated killer (LAK) cells.
Tumor diameters were measured daily and revealed that injection of
glioma-sensitized lymphocytes led to the elimination of
tumor while treatment with LAK cells had no therapeutic benefit. These results indicate, that at least for these two
glioma lines, gamma-IFN release, rather than in vitro cytotoxicity, was a better predictor for in vivo immunotherapeutic efficacy of the
glioma-sensitized, expanded T cells.