Figure 2: CTL and IFN- 𝛾 responses in mice immunized with fd bacteriophage particles in the presence or in the absence of CD4+ T cell help. Mice were immunized by two injections with either fdOV A 2 5 7 - 2 6 4 plus poly I:C or fdOV A 2 5 7 - 2 6 4 particles as indicated in Materials and Methods. Immunizations with fdOV A 2 5 7 - 2 6 4 particles were also performed in mice depleted of CD4+ T cells by treatment with GK1.5 mAb. CTL and IFN- 𝛾 productions were assayed after 15 days (a, b) or after two months (c, d) from the last injection. Each symbol represents data obtained from a single mouse. The mean value ± SD for each group is reported. (e) CD4+ T cell depletion was analyzed by cytofluorometry using noncompeting anti-CD4 antibody. The analysis was performed on spleen cells isolated from mice sacrificed at the time points indicated.