FACS analysis of splenic T cells co-stained with anti-CD8 and H-2Kd-GFP peptide pentamer indicate increased numbers of antigen specific CTLs in recombinant invasive E. coli vaccine immunized animals. Groups of four mice were vaccinated with GFP-expressing E.coli that were either non-invasive (GFP), recombinant invasive (GFP inv), or recombinant invasive with murine IL12 expression vector (GFP inv IL12). Negative controls included recombinant invasive E. coli with the murine IL12 expression vector but without the GFP antigen (()inv IL12), and PBS. Positive control vaccine was irradiated mouse macrophage RAW cell line (H-2d haplotype) constitutively expressing GFP (Raw/GFP). Vaccinated mice were boosted after two weeks, and splenocytes harvested after four weeks.