Purpose: In an effort to develop a successful immunotherapeutic treatment for ocular melanoma, we attempted to activate tumor-specific T cells using either B7.1 negative or positive tumor cells. B7.1 is an important costimulatory molecule that is normally present on antigen presenting cells and involved in stimulating the differentiation of CD8+ precursor cytotoxic T cells. We hypothesize that tumor cells genetically engineered to express B7.1 will activate tumor-specific T cells. Methods: Autologous peripheral blood lymphocytes were obtained on the day of enucleation and frozen until used. A tumor cell line was established by enzymatic digestion of ocular tumor tissue. Tumor cells were transfected by calcium phosphate precipitation with the episomal vector PBMG containing the human B7.1 cDNA. All transfected tumor cells expressed B7.1 by FACS analysis. Lymphocytes (0.3 × 106) were restimulated with 2 × 105 tumor cells plus recombinant IL-2 (either 25, 125, or 1000 u/ml) at weekly intervals for 10 weeks. The phenotype of proliferating lymphocytes was determined by FACS analysis using a series of T cell specific monoclonal antibodies (CD4, CD8, CD3, TCR). Tumor cell lysis was determined using a chromium release assay. Results: CD8+ T cells did not proliferate when restimulated with untransfected tumor cells and IL-2, and there was only a low-level, transient, proliferation of CD4+ T cells. The failure to either activate CD8+ T cells, or sustain CD4+ T cell proliferation, was not due to an insufficient concentration of IL-2. By contrast, B7.1 positive tumor cells induced sustained proliferation of both CD8+CD4- and CD8-CD4+ T cells. T cells lysed untransfected (B7.1 negative) autologous tumor cells, but failed to lyse HLA A,B,C class I incompatible ocular melanoma cells. Conclusions: Ocular melanoma cells are poor stimulators of CD8+ T cells, by contrast, B7.1 positive tumor cells activate tumor-specific T cells that lyse B7.1 negative tumor cells. These results imply that genetically engineered B7.1+ ocular melanoma cells may be used to immunize patients against development of metastatic tumors.
|Original language||English (US)|
|Journal||Investigative Ophthalmology and Visual Science|
|State||Published - Feb 15 1996|
ASJC Scopus subject areas
- Sensory Systems
- Cellular and Molecular Neuroscience