TNF and Dowling-Degos disease 1: Indeed, severity of DDD correlates with increased expression of inflammation mediators/markers in the IVD tissue (10), including interleukin-1 beta (IL-1β) (11), tumor necrosis factor-alpha (TNF-α) (12), interleukin-6 (IL-6), and interleukin-8 (IL-8) (13).