CD1d-deficient C57BL/6 mice, which selectively lack the natural killer (NK)-T cell population, also failed to form papillomas after inoculation with 6.8×1010 MusPV1 virions and a 3.5 month observation period (Figure 6F), indicating that ablation of this subset by itself is not sufficient to permit papilloma formation, in contrast to the crucial role of T cells. The gene discussed is CD1D; the disease is papilloma.