Fig. 2.
D7RM-1 prostate cancer cells are functionally deficient in antigen presentation to class I major histocompatibility complex (MHC)-restricted cytotoxic T lymphocytes (CTL). C57BL/6 mice (H-2b) were immunized with 107 plaque forming units control vector (V69, A) or β-gal–encoding recombinant vaccinia virus (rVV-β-gal, B). Splenocytes were prepared 3 weeks later and stimulated with β-gal peptide in vitro for a week to generate β-gal–specific CTL. The ability of target tumor cells to present antigen in a class I MHC-restricted manner to these β-gal–specific CTL was evaluated by means of chromium release cytotoxicity assay as described in the Materials and Methods section. Tumor target cells included those with β-gal (E22, D7RM-1) or without β-gal (EL4, RM-1). β-gal–expressing CT26.CL25 cell line (H-2d) was used as a control for class I MHC-restricted antigen presentation. E:T, effector to target.