PRF1 and neoplasm: Moreover, elderly tumor-associated CD8+ T cells demonstrated decreased perforin and IFN-γ implying reduced effector function; this is supported by our observation that elderly tumor-associated CTLs failed to up-regulate lytic function in response to IL-2/CD40, and represents another mechanism which reduces the efficacy of IL-2/CD40-mediated tumor regression in the elderly (26, 89, 90, 92).