Specificity of humoral anti-idiotype immune response. (A) Maximal anti-Fab^Id IgG titer increase after idiotype vaccination in all enzyme-linked immunosorbent assay responders compared with a fixed panel of 3 control Fab. (B) Binding of Fab^Id vaccination-induced antibodies to autologous and allogeneic tumor cells assessed by automated digital fluorescence microscopy. Bar graphs represent the percentage of tumor cells with surface-bound IgG. Photographs show autologous tumor cells incubated with prevaccination or postvaccination serum IgG. Red represents anti-CD19; green, anti-IgG; and blue, nuclear counterstain with DAPI.