Figure 4.

Prime and boost strategy using skin and intrarectal immunization regimens induces systemic and mucosal CTLs. BALB/c mice (n = 5) were immunized four times at 2-week intervals with no treatment or with 50 μg PCLUS3-IIIB peptide, 50 μg CT, and 50 μg CpG by the indicated route of administration: one intrarectal and then three transcutaneous immunizations (IR/TCI/TCI/TCI); three transcutaneous and then one intrarectal immunization (TCI/TCI/TCI/IR); four transcutaneous immunizations (TCI/TCI/TCI/TCI); or no treatment during the first three immunization intervals and an intrarectal immunization at the fourth interval (–/–/–/IR). On day 4 after the cell culture was established, CD8⁺ CTLs were purified by gradient centrifugation. Cytolytic activity of pooled SP (A) and PP (B) cells was measured in a ⁵¹Cr-release assay against P815 target cells alone (open symbols) or pulsed with P18-I10 peptide (filled symbols).