TNF alpha and IL-1 beta are separate targets in chronic arthritis.

Chronic arthritis is characterized by persistent joint inflammation and concomitant joint destruction. Using murine arthritis models and neutralizing antibodies as well as cytokine-specific knockout conditions, it was found that tumor necrosis factor alpha (TNF alpha) is important in joint swelling, whereas a direct role in tissue destruction is unlikely. Interleukin-1 (IL-1) is not a dominant cytokine in early joint swelling, but has a pivotal role in sustained cell infiltration and erosive cartilage damage. TNF alpha-independent IL-1 production is a prominent feature in murine arthritis models, implying that IL-1 as well as TNF alpha are appropriate targets for therapy. These observations provide evidence for the potential uncoupling of joint inflammation and erosive changes and underline the need for TNF alpha/IL-1 directed combination-therapy approaches.