C3 polymorphism, HLA and chronic renal failure in Spaniards

Systematic review of associations between HLA and renal function

Introduction

Kidney dysfunction is a highly significant disease, both in the United Kingdom and globally. Many previous studies have reported associations between human leukocyte antigens (HLA) and renal function; this systematic review attempts to identify, summarize and appraise all published studies of these associations.

Methods

A literature search was performed using Medline, Embase and Cochrane Central Register of Controlled Trials to identify papers whose keywords included each of the following concepts: HLA, renal failure and genetic association. A total of 245 papers were identified and assessed for eligibility; 35 of these were included in the final study.

Results

A total of 95 HLA types and 14 three‐locus haplotypes were reported to be associated with either increased or decreased renal function. A number of these findings were replicated by independent studies that reported 16 types were protective against renal dysfunction and 15 types were associated with reduced renal function. A total of 20 HLA types were associated with both increased risk of renal disease and decreased risk by independent studies.

Discussion

There is very little consensus on which HLA types have a protective or deleterious effect on renal function. Ethnicity may play a role, with HLA types possibly having different effects among different populations, and it is possible that the different primary diseases that lead to ESRD may have different HLA associations. Some of the studies may contain type I and type II errors caused by insufficient sample sizes, cohort selection and statistical methods. Although we have compiled a comprehensive list of published associations between renal function and HLA, in many cases, it is unclear which associations are reliable. Further studies are required to confirm or refute these findings.

Genetic polymorphism in C3 is associated with progression in chronic kidney disease (CKD) patients with IgA nephropathy but not in other causes of CKD

Objectives

The R102G variant in complement 3 (C3) results in two allotypic variants: C3 fast (C3F) and C3 slow (C3S). C3F presents at increased frequency in patients with chronic kidney disease (CKD), our aim is to explore its role in CKD progression and mortality.

Methods

Delta (Δ) eGFR for 2038 patients in the Salford Kidney Study (SKS) was calculated by linear regression; those with ≤-3ml/min/1.73m²/yr were defined as rapid progressors (RP) and those with ΔeGFR between -0.5 and +1ml/min/1.73m²/yr, labelled stable CKD patients (SP).A group of 454 volunteers was used as a control group. In addition, all biopsy-proven glomerulonephritis (GN) patients were studied regardless of their ΔeGFR. R102G was analysed by real-time PCR, and genotypic and allelic frequencies were compared between RP and SP along with the healthy control group.

Results

There were 255 SP and 259 RP in the final cohort. Median ΔeGFR was 0.07 vs. -4.7 ml/min/1.73m²/yr in SP vs. RP. C3F allele frequency was found to be significantly higher in our CKD cohort (25.7%) compared with the healthy control group (20.6%); p = 0.008.However, there was no significant difference in C3F allele frequency between the RP and SP groups. In a subgroup analysis of 37 patients with IgA nephropathy in the CKD cohort (21 RP and 16 SP), there was a significantly higher frequency of C3F in RP 40.5% vs. 9.4% in SP; p = 0.003. In the GN group, Cox regression showed an association between C3F and progression only in those with IgA nephropathy (n = 114);HR = 1.9 (95% CI 1.1–3.1; p = 0.018) for individuals heterozygous for the C3F variant, increased further for individuals homozygous for the variant, HR = 2.8 (95% CI 1.2–6.2; p = 0.014).

Conclusion

The C3 variant R102G is associated with progression of CKD in patients with IgA nephropathy.

Complement in basic processes of the cell

The complement system is reemerging in the last few years not only as key element of innate immunity against pathogens, but also as a main regulator of local adaptive responses, affecting dendritic cells as well as T and B lymphocytes. We review data showing that leucocytes are capable of significant autocrine synthesis of complement proteins, and express a large range of complement receptors, which in turn regulate their differentiation and effector functions while cross talking with other innate receptors such as Toll-like receptors. Other unconventional roles of complement proteins are reviewed, including their impact in non-leukocytes and their intracellular cleavage by vesicular proteases, which generate critical cues required for T cell function. Thus, leucocytes are very much aware of complement-derived information, both extracellular and intracellular, to elaborate their responses, offering rich avenues for therapeutic intervention and new hypothesis for conserved major histocompatibility complex complotypes.

Complement C3F allotype synthesized by liver recipient modifies transplantation outcome independently from donor hepatic C3

Complement component 3 (C3) presents both slow (C3S) and fast (C3F) variants, which can be locally produced and activated by immune system cells. We studied C3 recipient variants in 483 liver transplant patients by RT-PCR-HRM to determine their effect on graft outcome during the first year post-transplantation. Allograft survival was significantly decreased in C3FF recipients (C3SS 95% vs C3FS 91% vs C3FF 83%; P=.01) or C3F allele carriers (C3F absence 95% vs C3F presence 90%, P=.02). C3FF genotype or presence of C3F allele independently increased risk for allograft loss (OR: 2.38, P=.005 and OR: 2.66, P=.02, respectively). C3FF genotype was more frequent among patients whose first infection was of viral etiology (C3SS 13% vs C3FS 18% vs C3FF 32%; P=.04) and independently increased risk for post-transplant viral infections (OR: 3.60, P=.008). On the other hand, C3FF and C3F protected from rejection events (OR: 0.54, P=.03 and OR: 0.63, P=.047, respectively). Differences were not observed in hepatitis C virus recurrence or patient survival. In conclusion, we show that, independently from C3 variants produced by donor liver, C3F variant from recipient diminishes allograft survival, increases susceptibility to viral infections, and protects from rejection after transplantation. C3 genotyping of liver recipients may be useful to stratify risk.

Complement C3 Genotyping of Slow and Fast Variants by Real Time PCR-High Resolution Melting

“Slow” and “Fast” C3 complement variants (C3S and C3F) result from a g.304C>G polymorphism that changes arginine to glycine at position 102. C3 variants are associated with complement-mediated diseases and outcome in transplantation. In this work C3 genotyping is achieved by a Real Time PCR - High Resolution Melting (RT-PCR-HRM) optimized method. In an analysis of 49 subjects, 10.2% were C3FF, 36.7% were C3SF and 53.1% were C3SS. Allelic frequencies (70% for C3S and 30% for C3F) were in Hardy-Weinberg equilibrium and similar to those published previously. When comparing RT-PCR-HRM with the currently used Tetraprimer-Amplification Refractory Mutation System PCR (T-ARMS-PCR), coincidence was 93.8%. The procedure shown here includes a single primer pair and low DNA amount per reaction. Detection of C3 variants by RT-PCR-HRM is accurate, easy, fast and low cost, and it may be the method of choice for C3 genotyping.

Human genetic variation in the Sierra de Gredos mountain (central Spain): study of several polymorphisms

The variation in the third component of human complement (C3) and orosomucoid (ORM1) serum proteins, and 6-phosphogluconate dehydrogenase (6PGD), adenosine deaminase (ADA), esterase D (ESD), and acid phosphatase (ACP1) red cell enzymes was examined in two samples from autochthonous populations living on either side of the Sierra de Gredos range in Central Spain. These results support only a moderate differentiation between Gredos subpopulations, which is discussed in relation to other Iberian Peninsula groups. Allele frequencies in Gredos show a remarkable heterogeneity as contrasted with other Iberian populations for most of the markers examined; relatively high C3*S, ORM1*F, ADA*1, ESD*2, and ACP1*C gene frequencies are characteristics of Gredos samples. This differentiation was more marked for the Northern Gredos population and could be related to the geographical peculiarities of this region.

Frequency of complement third component (C3) and properdin factor (BF) phenotypes in patients with various clinical manifestations of HBV infection

Four groups of children were tested for the distribution of C3 and BF phenotypes: HBV-infected patients with Gianotti-Crosti syndrome, with CAH and with glomerulonephritis, and healthy children. The frequency of the phenotype C3F was significantly higher in children with Gianotti-Crosti syndrome in comparison with healthy children. The frequency of the phenotype BFS was significantly higher in patients with glomerulonephritis than in individuals with CAH. The difference between the frequency of the BFS phenotype in glomerulonephritis patients and that in healthy subjects neared significance. We suggest that the carriers of these phenotypes are characterized by susceptibility to some immune complex diseases associated with HBV infection.

Phenotype distribution of the third component of complement (C3) and of the properdin B factor (BF) in children with mumps meningitis

The C3 and BF phenotype frequencies were studied in children with mumps meningitis. No significant differences were found between this group and other groups; children with mumps without meningitis and healthy children.

HLA frequencies in Basques in Spain and in neighbouring populations

HLA antigen and gene frequencies at the A, B, and C loci are examined in a sample of 181 Basques and 102 non-Basques in Bilbao, Spain. The most common associations of genes at the A and B loci are as in western Europe generally. The results are compared with gene frequencies in other Basque and non-Basque samples in Spain and France. There is clear distinction in gene frequency between Basques and non-Basques, to which the greatest contribution is made by A1 and B35, followed by B7, B8 and B12; and a difference between Basques in France and in Spain, notably in A28, 29, 30 and 31 and B17 and 18.

Exclusive HLA-DQ factors do not explain susceptibility to insulin-dependent diabetes

DQA1, DQA2, DQB1, and DRB1 alleles have been determined and the DQA1 and DQB1 DNA gene sequences assigned by using restriction fragment length polymorphisms in 67 diabetic individuals and 72 controls. It has been found that: 1) DQA2 (U allele) is not a susceptibility factor, 2) non-aspartic acid homozygosity in residue 57 (Asp 57 negative) of the DQ beta chains is positively correlated with insulin-dependent diabetes mellitus (IDDM), and 3) DQ beta Asp-57-negative and DQ alpha arginine-52-positive (Arg-52-positive) individuals are increased among diabetic patients; this latter analysis shows a higher etiologic fraction (delta) value than the one obtained when considering only homozygous DQ beta Asp-57-negative individuals. However, if only non-DR3 or DR4 individuals were considered (both in DQ beta Asp-57-negative homozygous and in DQ beta Asp-57-negative/DQ alpha Arg-52-positive individuals) the correlation with disease disappears. In addition, the postulated risk DQ beta Asp 57-negative and DQ alpha Arg 52 positive is absent in six patients. These data do not discard the possibility that DR3/DR4 may contain the primary susceptibility factors. It is concluded that it is not possible to assign the susceptibility to IDDM to a specific HLA locus and that several loci within the same or the trans haplotype may be involved.

C3 and Bf complement types in chronic renal failure

C3 and BF allele frequencies were studied in 55 patients with idiopathic membranous nephropathy (IMN) and unrelated normal individuals from North-East England. Eighteen of these IMN patients progressed to renal failure and C3*S allele showed a significant increase in these patients. A possible mechanism for this increase is briefly discussed.