Lupus nephritis: from pathogenesis to targets for biologic treatment.

BACKGROUND/AIMS Lupus nephritis is an organ manifestation of systemic autoimmunity. Current treatment algorithms are still based on unselective immunosuppressive drugs. There is hope that highly selective biological drugs could be as or even more effective but less toxic. A profound understanding of the pathogenesis of lupus nephritis is necessary to identify the optimal molecular targets. METHODS PubMed and www.clincialtrials.gov were searched using 'lupus nephritis' as the key word. RESULTS The pathogenesis of lupus nephritis is based (1) on the mechanisms that lead to loss of tolerance against nuclear autoantigens, i.e. systemic lupus, and then (2) on the mechanisms of immune complex-induced intrarenal inflammation. Systemic lupus develops when genetic variants allow autoimmunization against nuclear autoantigens, e.g. by impairing lymphocyte depletion via apoptosis, opsonization, and rapid phagocytic clearance. This allows endogenous nucleic acids to directly activate Toll-like receptors on dendritic cells or B cells, a process that drives IFN-α-driven immunity, antigen presentation, and the activation of autoreactive lymphocyte subsets. Activation of B cells and their maturation to plasma cells promotes autoantibody production and subsequent immune complex glomerulonephritis. Complement and numerous proinflammatory cytokines drive the inflammatory process that can cause kidney injury, scarring, and chronic kidney disease. CONCLUSION Systemic lupus is more a variable syndrome than a single disorder based on heterogeneous genetic variants and complex aberrant immune alterations. This makes it less likely that a single specific biological drug will be as efficient as currently used unselective immunosuppressive drugs. Autoantibody production and intrarenal immune complex formation are the hallmark of lupus nephritis. However, kidney injury and scarring also result from local amplification of tissue inflammation. Therefore, a combination of unselective immunosuppressive and biological drugs that block immune cell recruitment or proinflammatory cytokines may be promising to improve disease outcomes in lupus nephritis.