Since neither GL261 nor CT2A tumor antigens have been well characterized, we needed to utilize GBM cells, engineered to express the GP33 (gp33-41), a model tumor antigen from Lymphocytic Choriomeningitis Virus (LCMV) glycoprotein to measure cytotoxic CD8+ T cells specific to tumor (GP33) and HSV antigens (gB498-505) in both blood and in the brain of mice using peptide-MHC-I (pMHC) tetramers16,21. The gene discussed is CD8A; the disease is glioblastoma.