BACKGROUND: Lupus nephritis (LN) is a disease marked by autoantibodies against complement components. Autoantibodies against negative complement regulator factor H (anti-FH) are prevalent in aHUS, are associated with deletion of factor H-related protein 1 (FHR1) gene, and have overt functional consequences. They are also observed in C3 glomerulopathies. The frequency and relevance of anti-FH in LN are poorly studied.
OBJECTIVE: The aim of our investigation was to screen for the presence of anti-FH and FHR1 gene deletion in a cohort of LN patients and to evaluate their association with LN activity.
METHODS: ELISA test and Western blot for detection of anti-FH and FHR1 deletion were used, respectively. Patients\' clinical and laboratory parameters regarding anti-FH role were processed by statistical analysis.
RESULTS: Anti-FH were found at low level in a small number of LN patients - 11.7% (7/60) and were not associated with deletion of FHR1. Anti-FH did not correlate with ANA titers, anti-dsDNA, C3/C4 hypocomplementemia, eGFR, proteinuria, or active urinary sediment in LN patients. A weak correlation was found between anti-FH and anti-C3 levels. Anti-FH were linked with endocapillary proliferation and histological activity index. Four anti-FH positive patients had severe to moderate LN as per the BILAG renal score.
CONCLUSIONS: Anti-FH autoantibodies are an accessory finding in LN and are more likely to manifest during the active phase of the disease. Due to their low frequency and plasma levels, they do not seem suitable for routine laboratory investigation in patients with LN.

There is a little information about of expression of C4d (complement fragment) in Focal segmental glomerulosclerosis (FSGS) subtypes. Our aim was to determine the expression of C4d in FSGS subtypes in percutaneous native renal biopsies in a second-level hospital and its correlation with clinical, biochemical and histological variables.
A retrospective study in paraffin blocks of patients with biopsy with FSGS aged 16-65 years, indistinct sex, not diabetic or obese. Immunohistochemistry was performed for C4d and their expression was analyzing in non-sclerosed glomerular capillaries (GC) and sclerosis areas (SA). Clinical and biochemical variables were recorded. The cases were divided into C4d positive and C4d negative groups and compared. The correlation between C4d staining scores in CG and SA with clinical and biochemical variables were analyzed.
Twenty samples were analyzed, 4 for each subtype. At the time of biopsy average age 38.8 ± 18.6 years, 65% male, 8.7% were hypertension. The percentage of positivity for C4d was 40% in GC, 30% SA and 35% in mesangium. The highest expression was for cellular and collapsing subtypes. C4d positivity cases had increased proteinuria (p = 0.035). A significant correlation was found between percentage of C4d expression in CG with SA (p = 0.012) and SA with tubular atrophy and interstitial fibrosis (p < 0.05).
C4d expression in FSGS predominated in the cellular and collapsing subtypes, which translates complement activation. C4d is a possible surrogate marker in GSFS.

Antineutrophil cytoplasmic antibody-associated vasculitides are primary vasculitides that affect small vessels in various organs, including the kidney. Renal involvement is characterized by the presence of glomerulonephritis with crescents and necrosis in light microscopy and a pauci-immune pattern in immunofluorescence. The participation of complement in the pathogenesis of these entities has been valued in recent years, initially in animal models and later in studies in humans, by demonstrating the presence of fragments of the alternative complement pathway, in plasma and urine, together with complement deposits in glomeruli and small vessels of patients affected by antineutrophil cytoplasmic antibody vasculitis. The presence of complement in these entities confers a worse general and renal prognosis.

Autoimmune haemolytic anaemias (AIHA) are acquired haematological disorders caused by increased peripheral erythrocyte destruction mediated by autoantibodies against erythrocyte antigens. They classified according to aetiology into primary and secondary, and according to the type of antibody and reaction temperature into AIHA due to warm antibodies (w-AIHA) and AIHA due to cold antibodies (c-AIHA). The mainstay of management in w-AIHA remains glucocorticoid therapy, and the early addition of rituximab has shown good results in recent studies. Primary c-AIHA is mainly treated with rituximab, alone or in combination with chemotherapy. New drugs such as Syk inhibitors, anti-FcRn Ig and complement inhibitors are in advanced development and will expand the therapeutic arsenal, especially in refractory or relapsed cases.

The complement system is a first line of defence against infectious, tumoral or autoimmune processes, and it is constitutively regulated to avoid excessive or unspecific activation. Factor H (FH), a most relevant complement regulator, controls complement activation in plasma and on the cellular surfaces of autologous tissues. FH shares evolutionary origin and structural features with a group of plasma proteins known as FH-Related Proteins (FHRs), which could act as FH functional antagonists. Studies in patient cohorts of atypical Haemolytic-Uraemic Syndrome (aHUS), C3 Glomerulopathy (C3G), and IgA nephropathy (IgAN), have identified rare genetic variants that give rise to severe FH and FHRs dysfunctions, and are major genetic predisposing factors. These patients also have a higher frequency of a few polymorphisms whose relevance as disease risk factors is incompletely understood. In the last years, the availability of specific reagents has allowed a more precise quantitation of FH and FHRs in plasma samples from patients and controls. These studies have revealed that some aHUS, C3G or IgAN risk polymorphisms determine mild changes in FH or FHRs levels that could somehow perturb complement regulation and favour disease pathogenesis.

The complement system is a first line of defence against infectious, tumoral or autoimmune processes, and it is constitutively regulated to avoid excessive or unspecific activation. Factor H (FH), a most relevant complement regulator, controls complement activation in plasma and on the cellular surfaces of autologous tissues. FH shares evolutionary origin and structural features with a group of plasma proteins known as FH-Related Proteins (FHRs), which could act as FH functional antagonists. Studies in patient cohorts of atypical Haemolytic-Uraemic Syndrome (aHUS), C3 Glomerulopathy (C3G), and IgA nephropathy (IgAN), have identified rare genetic variants that give rise to severe FH and FHRs dysfunctions, and are major genetic predisposing factors. These patients also have a higher frequency of a few polymorphisms whose relevance as disease risk factors is incompletely understood. In the last years, the availability of specific reagents has allowed a more precise quantitation of FH and FHRs in plasma samples from patients and controls. These studies have revealed that some aHUS, C3G or IgAN risk polymorphisms determine mild changes in FH or FHRs levels that could somehow perturb complement regulation and favour disease pathogenesis.

BACKGROUND: Correctly identifying patients with biliary atresia (BA), while avoiding invasive diagnostic methods is challenging. The purpose of this study was to determine the value of serum immune indicators for distinguishing BA from other causes of cholestasis in infants.
METHODS: The data of infants with a surgical/histological diagnosis of BA and those with other causes of cholestatic jaundice were retrospectively analyzed. Patients were divided into a BA group and a cholestasis control (CC) group. Biochemical parameters, major lymphocyte subsets, immunoglobin and C3 and C4 complement levels were compared between the groups.
RESULTS: A total of 129 infants with BA and 63 with other causes of cholestasis (CC control group) with a median age of 2.2 months were included in the analysis. The levels of CD3+ T cells, CD3+CD4+ T cells, and premature T cells and the levels of C3 and C4 were all significantly higher in the BA group compared to the CC group (all P<0.05). Pair-wise correlation analyses indicated that C3 and C4 had a significant positive correlation with γ-GT in the BA group, but not in the CC group. Five indices were found to be significantly associated with BA: stool color, globulin, γ-GT, C3 and C4. A model incorporating stool color, gamma-glutamyl transpeptidase level, and C3 level exhibited an area under the ROC curve (AUC) of 0.93, and a sensitivity of 93% and specificity of 83% for the diagnosis of BA.
CONCLUSIONS: Models incorporating serum C3 levels may be useful for accurately diagnosing BA in infants.

The activation of the alternative pathway of the complement is involved in the development of several renal diseases, such as atypical haemolytic uremic syndrome and C3 glomerulopathy. In C3 glomerulopathy, a high percentage of patients have circulating levels of the autoantibody called C3NeF, which causes systemic dysregulation of the complement system. In some cases, the presence of this antibody has been related with abnormalities of adipose tissue, causing acquired partial lipodystrophy (Barraquer-Simons syndrome). Acquired partial lipodystrophy is an extremely rare disorder affecting the distribution of subcutaneous adipose tissue and that mainly onsets during childhood. These patients, in addition to possibly presenting with all the metabolic disorders associated with the adipose tissue defect, present with C3 hypocomplementemia and C3NeF and 25% have developed C3 glomerulopathy. Although it has been known for some time how the dysregulation of the complement system affects the kidneys, it remains unknown how it exactly affects adipose tissue; nevertheless, the relationship is quite clear. In this paper, we describe the connection between the complement system with the biology of the adipose tissue and its pathogenesis reflected from acquired partial lipodystrophy.

Disseminated gonococcal infection is a rare presentation of the sexually transmitted pathogen, Neisseria gonorrhoeae. Here, we report the case of a 64-year-old woman with disseminated gonococcal infection, which started with symptoms of oligoarthritis and malaise. Neisseria gonorrhoeae was identified in the carpal synovial fluid. The follow-up study revealed an absence of total hemolytic complement and complement C2 was not detected. Being relatively common, C2 deficiency has been associated with disseminated gonococcal infection in a few cases. We present a new case and discuss those previously published.

Type iii extracapillary glomerulonephritis (PEGN) is a common cause of rapidly progressive glomerulonephritis and it is usually associated with circulating anti-neutrophil cytoplasmic antibodies (ANCAs). Recent evidence points to complement activation as an important factor in the pathogenesis of PEGN. The aim of the present study was to assess the value of C3 deposits in the prognosis of PEGN.
All patients diagnosed of PEGN from 1995 to 2015 (n=72) were included in this study. Progression of renal disease in patients with positive staining for C3 by immunofluorescence was compared with those with negative staining. Mean follow up was 73 months. Progression to end-stage renal disease in relation to clinical and histological variables was analyzed.
Positive staining for C3 was observed in 22 out of the 72 patients (30.5%). At the time of diagnosis, patients with C3 deposits had higher serum creatinine concentration than those without C3 staining (5.00 vs. 3.85mg/dl, P=0.050). Renal survival at 10 years was 36.9% in patients with positive C3 staining vs. 64.4% in patients with negative staining (P=0.005). Mortality at 10 years was higher in patients with C3 deposits than in patients without deposits (77 vs. 49.3%).
Thus, our study shows that PEGN with deposits of C3 is associated with worse renal prognosis and greater mortality. These results would support the hypothesis that activation of the alternative pathway complement may play an important role in the generation of renal injury associated with PEGN.