Impact of C4, C4A and C4B gene copy number variation in the susceptibility, phenotype and progression of systemic lupus erythematosus

Abstract Background Complement component 4 (C4) gene copy number (GCN) affects the susceptibility to systemic lupus erythematosus (SLE) in different populations, however the possible phenotype significance remains to be determined. This study aimed to associate C4A , C4B and total C4 GCN and SLE, focusing on the clinical phenotype and disease progression. Methods C4 , C4A and C4B GCN were determined by real-time PCR in 427 SLE patients and 301 healthy controls, which underwent a detailed clinical evaluation according to a pre-established protocol. Results The risk of developing SLE was 2.62 times higher in subjects with low total C4 GCN (< 4 copies, OR = 2.62, CI = 1.77 to 3.87, p < 0.001) and 3.59 times higher in subjects with low C4A GCN (< 2 copies; OR = 3.59, CI = 2.15 to 5.99, p < 0.001) compared to those subjects with normal or high GCN of total C4 (≥4) and C4A (≥2), respectively. An increased risk was also observed regarding low C4B GCN, albeit to a lesser degree (OR = 1.46, CI = 1.03 to 2.08, p = 0.03). Furthermore, subjects with low C4A GCN had higher permanent disease damage as assessed by the Systemic Lupus International Collaborating Clinics - Damage Index (SLICC-DI; median = 1.5, 95% CI = 1.2-1.9) than patients with normal or high copy number of C4A (median = 1.0, 95% CI = 0.8-1.1; p = 0.004). There was a negative association between low C4A GCN and serositis ( p = 0.02) as well as between low C4B GCN and arthritis ( p = 0.02). Conclusions This study confirms the association between low C4 GCN and SLE susceptibility, and originally demonstrates an association between low C4A GCN and disease severity.

Pesquisa de fração c4d e imunoglobulina para tratamento da rejeição aguda mediada por anticorpos no transplante renal / Search of c4d fraction and immunoglobulin for treatment of acute rejection mediated by antibodies in the Kidney transplantation

A rejeição aguda mediada por anticorpos, diagnosticada pela deposição de C4d na biópsia do enxerto, é uma complicação grave do transplante renal, com taxas históricas de perda do órgão transplantado da ordem de 30% -50%. Ainda que não existam ensaios clínicos adequadamente conduzidos para avaliar o papel da imunoglobulina no tratamento da RMA, a evidência proveniente de séries de casos publicadas por centros especializados aponta para uma taxa de preservação do enxerto em um ano de até cerca de 90% em com o uso da imunoglobulina humana intravenosa, sobretudo quando associada à plasmaférese, resultado esse muito superior ao controle histórico sem uso de imunoglobulina. Diante disso, recomenda-se a inclusão da imunoglobulina humana intravenosa no CEAF para o tratamento da rejeição aguda mediada por anticorpos comprovada por biópsia (presença de depósitos de C4d) pós-transplante renal, refratária a corticoide e OKT3. Não há evidências suficientes para recomendar um regime preferencial de administração de imunoglobulina em relação aos demais. Recomenda-se o regime mais estudado, constituído de imunoglobulina humana 500 mg/Kg/dia por até sete dias, quando utilizada isoladamente, ou 500 mg/Kg/dia em dias alternados, quando associada à plasmaférese. Recomendação da CONITEC: Os membros da CONITEC presentes na 7ª reunião ordinária do dia 02/08/2012 recomendaram a incorporação da pesquisa de fração C4d e da imunoglobulina para o tratamento da rejeição aguda mediada por anticorpos no transplante renal, conforme PCDT a ser elaborado pelo Ministério da Saúde. A Portaria SCTIE/MS Nº 36, de 27 de setembro de 2012 - Torna pública a decisão de incorporar a imunoglobulina para tratamento da rejeição aguda mediada por anticorpos no transplante renal e o exame de pesquisa da fração C4d no Sistema Único de Saúde.

Diagnosis of acute humoral rejection using immunofluorescence in renal allograft biopsies- one step towards better understanding!

Immunofluorescence (IF) studies are important diagnostic tool in understanding pathogenesis involved in graft injury. Acute humoral rejection (AHR) associated with circulating donor-specific cytotoxic antibodies, is a poor prognosticator for graft survival. It can be diagnosed by staining for C4d antibody using indirect IF technique. C4d staining required to diagnose AHR was made mandatory for reporting renal allograft biopsies in 7th Banff conference. We present 2 years experience of IF studies using C4d polyclonal antibody on 546 renal allograft biopsies belonging to two groups of patients; 464 from group A (tolerance induction protocol) and 82 from group B (controls). We observed C4d focal positivity in 4 (0.9%) biopsies from group A and 4 (4.9%) from group B. We conclude that it is advisable to collect simultaneous core biopsy samples for IF studies and light microscopy to give better definition of allograft injury and thereby support in clinical management.

Activation of Intrarenal Complement System in Mouse Model for Chronic Cyclosporine Nephrotoxicity

PURPOSE: Local activation of the complement system plays a role in target organ damage. The aim of our study was to investigate the influence of cyclosporine (CsA)- induced renal injury on the complement system in the kidney. MATERIALS AND METHODS: Mice fed a low salt (0.01%) diet were treated with vehicle (VH, olive oil, 1mL/kg/day) or CsA (30mg/kg/day) for one or four weeks. Induction of chronic CsA nephrotoxicity was evaluated with renal function and histomorphology. Activation of the complement system was assessed through analysis of the expression of C3, C4d, and membrane attack complex (MAC), and the regulatory proteins, CD46 and CD55. CsA treatment induced renal dysfunction and typical morphology (tubulointerstitial inflammation and fibrosis) at four weeks. RESULTS: CsA-induced renal injury was associated with increased the expression of C3, C4d, and MAC (C9 and upregulation of complement regulatory proteins (CD 46 and CD55). Immunohistochemistry revealed that the activated complement components were mainly confined to the injured tubulointerstitium. CONCLUSION: CsA-induced renal injury is associated with activation of the intrarenal complement system.

Peritubular Capillary C4d Deposition in Chronic Allograft Dysfunction

Peritubular capillary (PTC) C4d staining represents a marker for acute humoral rejection, however, the impact of positive staining on chronic allograft dysfunction has received little attention. Ninety-three renal allograft biopsies from 93 patients were selected from a total of 174 renal allograft biopsies, which were obtained 6 months or more after transplantation (median: 89 months). Fresh frozen renal tissue was stained with monoclonal antibody against C4d. Sixteen of 93 biopsies showed C4d staining in PTC. C4d staining was positive in 40% of acute rejection cases (n=15) and 21% of chronic rejection cases (n=24). When the samples were divided according to C4d positivity, the C4d (+) group had a higher proportion of acute rejection than the C4d (-) group. However, no significant difference was observed between the two groups in terms of the prevalence of chronic rejection. Degrees of histological injury including tubulitis, interstitial inflammation and interstitial fibrosis were not significantly different between C4d (+) and C4d (-) groups. However, the 2-year graft survival rate after biopsy was lower in the C4d (+) group than in the C4d (-) group (24.8% versus 59.0%, p=0.1255). C4d staining in PTC is associated with late acute rejection, but not with chronic rejection based on conventional morphologic criteria in patients with chronic allograft dysfunction.