Induction of GFP-specific immune response in GFP LV-injected mice. (A) T-cell lines derived from splenocytes of C57BL/6 mice killed at different times after injection of CMV-GFP LV were tested for GFP-specific IFN-γ production by ELISA. IFN-γ produced in control experiment performed in the absence of GFP was subtracted from that produced in the presence of GFP. (B) Freshly isolated T cells 1 week after injection from PBS- (white bar, n = 3) and LV-GFP–injected mice (black bar, n = 3) were directly tested in ELISPOT assay for IFN-γ production in response to GFP. The percentage of CD8⁺ T cells present during the ELISPOT assay was determined by FACS analysis. One representative experiment of 3 performed is shown. Means ± SD are shown.