Figure 2.

Unhelped primary cytotoxic T lymphocytes (CTLs) generated from higher precursor frequency (PF) have therapeutic effect against early established tumours. (a) An experimental design. Wild-type (WT) B6 or Ia^b−/− mice were first challenged with BL6-10_OVA 3 days (early tumour burden) or 6 days (late tumour burden) before ovalbumin (OVA) -pulsed dendritic cells (DC_OVA) immunization. One day before immunizing, the endogenous-PF of all these mice was increased by transferring OTI CD8⁺ T cells. Twenty-four days after challenge, all the groups were assessed for tumour protection. (b) Impact of higher PF on the efficacy of DC_OVA immunization in early established tumours. Gross pathology of lungs showing relative surface tumour burden. (c) To determine whether protection is a result of effector CTL recruitment, the infiltration of interferon-γ-positive (IFN-γ⁺) CTLs in the lungs of some immunized mice was determined by intracellular staining assay. The values represent frequencies of IFN-γ⁺ CTL in the total CD8⁺ T-cell population, and are cumulative of two independent studies with two or three mice per group. The horizontal bars indicate means. **P < 0·01, versus Iab^−/− with endogenous-PF. (d) Impact of higher PF on the efficacy of DC_OVA immunization in late-established tumours. Gross pathology of lungs showing relative surface tumour burden. The results in (b) and (d) are cumulative of two independent studies with four mice per group.