Cytokines in autoimmune bullous skin diseases. Epiphenomena or contribution to pathogenesis?

An increasing number of publications reports altered expression of numerous cytokines in autoimmune bullous skin diseases. However, with few exceptions, the pathogenic relevance of increased levels in serum and blister fluid as well as elevated cytokine expression in the skin has not been addressed. The introduction of TNFa inhibition into the treatment of several chronic inflammatory and autoimmune diseases has clearly demonstrated the potential of an anticytokine-based therapy. As the treatment of autoimmune bullous skin diseases remains a therapeutic challenge, introduction of novel treatment options for these patients is needed. Therefore, we here present the current understanding of the role of cytokines in autoimmune bullous skin diseases; focusing on pemphigus vulgaris and bullous pemphigoid as representative autoimmune bullous skin diseases, and on the cytokines TNFα, IL-1 and IL-6, as respective inhibitory compounds have been licensed. Increased levels of these 3 chemokines have been found in both sera and blister fluid of patients with pemphigus vulgaris and bullous pemphigoid, and for most, disease activity correlates with cytokine levels. In animal models of pemphigus vulgaris, deficiency of IL-1 or TNFa partially protects from pemphigus IgG-induced blister formation. For bullous pemphigoid, circumstantial experimental evidence suggests, that inhibition of TNFα, IL-1 and IL-6 might be a suitable approach to dampen the inflammatory response. These assumptions are supported by reports of a therapeutic benefit of TNFa inhibition in treatment-refractory cases of pemphigus and several pemphigoid diseases. In summary, the current understanding of the contribution of chemokines to autoimmune bullous skin diseases, does not allow to draw final conclusions. A more detailed understanding of the chemokine network in these disorders is required and may be provided by the correspond-ing experimental models.