TNF and neoplasm: described the adverse outcome pathway (AOP) for skin sensitization resulting from degradation of tattoo inks, where the degradation products form haptens by attaching to skin proteins (initiating event), followed an immunogenic response with release of IL-18 and TNF-α causing sensitization, activation of antigen-presenting immune cells (such as Langerhans cells), followed by activation of T cells and subsequent immune response [46].