Vaccines prepared in a cell-free system are capable of inducing an immune response that recognizes the native 38C13 protein on the cell surface. Flow cytometry was used to analyze 38C13 tumor cells incubated with mouse sera obtained after 3 vaccinations with the indicated proteins. Each histogram represents results from one mouse. The scale shows fold change over secondary antibody alone on a log2 scale. The numbers in the upper right corner of each box indicate mean median fluorescence for that group. (A) Flow cytometry of cells incubated with sera at a 1:20 dilution. (B) Analysis of an independent experiment by flow cytometry. Cells were incubated with sera at a 1:800 dilution to determine the relative efficacy of vaccines in induction of a specific Ab response. **Significance (P < .05) by Student 2-tailed t test compared with both 38C13 scFv (VH-VL) and A20 scFv (VH-VL) and *statistical significance (P < .05) compared with A20 scFv (VH-VL).
