Comprehensive approach to study complement C4 in systemic lupus erythematosus: Gene polymorphisms, protein levels and functional activity.

Genetic variation of the genes encoding complement component C4 is strongly associated with systemic lupus erythematosus (SLE), a chronic multi-organ auto-immune disease. This study examined C4 and its isotypes on a genetic, protein, and functional level in 140 SLE patients and 104 healthy controls. Gene copy number (GCN) variation, silencing CT-insertion, and the retroviral HERV-K(C4) insertion) were analyzed with multiplex ligation-dependent probe amplification. Increased susceptibility to SLE was found for low GCN (≪2) of C4A. Serositis was the only clinical manifestation associated with low C4A GCN. One additional novel silencing mutation in the C4A gene was found by Sanger sequencing. This mutation causes a premature stop codon in exon 11. Protein concentrations of C4 isoforms C4A and C4B were determined with ELISA and were significantly lower in SLE patients compared to healthy controls. To study C4 isotypes on a functional level, a new C4 assay was developed, which distinguishes C4A from C4B by its binding capacity to amino or hydroxyl groups, respectively. This assay showed high correlation with ELISA and detected crossing over of Rodgers and Chido antigens in 3.2% (8/244) of individuals. The binding capacity of available C4 to its substrates was unaffected in SLE. Our study provides, for the first time, a complete overview of C4 in SLE from genetic variation to binding capacity using a novel test. As this test detects crossing over of Rodgers and Chido antigens, it will allow for more accurate measurement of C4 in future studies.

Systemic lupus erythematosus: review of synthetic drugs.

INTRODUCTION: Synthetic drugs are prescribed for nearly all patients with systemic lupus erythematosus (SLE), a multisystem autoimmune disease, to ameliorate symptoms and positively influence outcome. While only 2 biologic agents have been approved for the treatment of SLE, synthetic drugs are still the mainstay of therapy in SLE. The highly variable and unpredictable course of SLE poses a challenge for physicians as to what drug(s) should be prescribed for which patient. AREAS COVERED: Previous and recent studies have evaluated several synthetic drugs in the treatment of SLE. This article reviews currently available evidence for the efficacy and safety of synthetic drugs in SLE and discusses future treatment perspectives. EXPERT OPINION: Hydroxychloroquine should be considered an anchor drug in SLE because of the multiple beneficial effects of this agent. When patients present with persistent disease activity despite hydroxychloroquine therapy or need higher dosages and/or prolonged use of glucocorticoids (GCs), additional immunosuppressants should be promptly prescribed. Based on available evidence, azathioprine and mycophenolate mofetil are the drugs of first choice. Determination of a 'safe' GC dose for chronic daily use is of major importance and should be subject of further studies in large patient populations.