The immunological activities of IFN-λs have been investigated to show that IFN-λs upregulated expression levels of the class I molecules of the major histocompatibility complexes (MHC; Kotenko et al, 2003; Li et al, 2009), and that local secretion of IFN-λ2 from tumours enhanced cell-mediated immunity against the tumours by augmenting activities of natural killer (NK) cells and cytotoxic T cells (Sato et al, 2006; Numasaki et al, 2007). The gene discussed is IFNL2; the disease is neoplasm.