The frequency dependence of non-sequential double ionization (NSDI) of Ne is studied using a semiclassical rescattering model. It is found that the ratio (Ne2+/Ne+), calculated for a laser intensity of 1.0 × 1015 W cm−2, increases while the wavelength decreases down to about 250 nm, the limit of the applied model. Careful investigations of the trajectories show that there are two categories of double ionization: ‘instant ionization’ and ‘delayed ionization’. By limiting the time interval between the re-collision time and ionization time, the ‘delayed ionization’ is identified to give rise to the high probability of NSDI in the short wavelength region.

T-cell priming is strongly affected by the longevity of antigenbearing dendritic cells (DCs), which are typically short-lived in lymphoid tissues. 'Survival gene' Bcl-xl is critical for the lifespan of DCs in vivo. Here, we showed that in vivo coadministration of Bcl-xl under control of the DC-specific promoter (CD11c-Bcl-xl) and TRP2hsp70 DNA prolonged T-cell stimulation by DCs and augmented TRP2-specific-IFNg-producing CD8+ T-cell responses. Consistent with these findings, enhanced protection and significant therapeutic immunity to B16 melanoma was generated by this coimmunization strategy, which also augmented therapeutic immunity to GL-26 tumor. In this B16 melanoma model, results from animal experiments with depletion of immune cells indicate that CD8+ T cells and NK cells are important in the antitumor immunity induced by this coimmunization strategy. These observations suggest that 'survival gene' Bcl-xl potentiates the magnitude of antigen-specific-CD8+ T-cell responses and the efficacy of antitumor immunity induced by DNA vaccine, and is relevant for the design of in vivo targeted DC-based vaccine strategies to improve immunity against cancer. Gene Therapy (2005) 12, 1517-1525.

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