Genetic aspects of rheumatic diseases

Copy number variation of the gene NCF1 is associated with rheumatoid arthritis

AIMS

The aim of this study was to investigate genetic variants in the gene neutrophil cytosolic factor 1 (NCF1) for association with rheumatoid arthritis (RA). In rodent models, a single-nucleotide polymorphism (SNP) in Ncf1 has been shown to be a major locus regulating severity of arthritis. Ncf1 encodes one of five subunits of the NADPH oxidase complex. In humans the genomic structure of NCF1 is complex, excluding it from genome-wide association screens and complicating genetic analysis. In addition to copy number variation of NCF1, there are also two nonfunctional pseudogenes, nearly identical in sequence to NCF1. We have characterized copy number variation and SNPs in NCF1, and investigated these variants for association with RA.

RESULTS

We find that RA patients are less likely to have an increased copy number of NCF1, 7.6%, compared with 11.6% in controls; p=0.037. We also show that the T-allele of NCF1-339 (rs13447) is expressed in NCF1 and significantly reduces reactive oxygen species production.

INNOVATION

This is the first finding of genetic association of NCF1 with RA. The detailed characterization of genetic variants in NCF1 also helps elucidate the complexity of the NCF1 gene.

CONCLUSION

These data suggest that an increased copy number of NCF1 can be protective against developing RA and add support to previous findings of a role of NCF1 and the phagocyte NADPH oxidase complex in RA pathogenesis.

Neuroimmune interaction in inflammatory diseases

The inflammatory response is modulated through interactions among the nervous, endocrine, and immune systems. Intercommunication between immune cells and the autonomic nervous system is a growing area of interest. Spatial and temporal information about inflammatory processes is relayed to the central nervous system (CNS) where neuroimmune modulation serves to control the extent and intensity of the inflammation. Over the past few decades, research has revealed various routes by which the nervous system and the immune system communicate. The CNS regulates the immune system via hormonal and neuronal pathways, including the sympathetic and parasympathetic nerves. The immune system signals the CNS through cytokines that act both centrally and peripherally. This review aims to introduce the concept of neuroimmune interaction and discuss its potential clinical application, in an attempt to broaden the awareness of this rapidly evolving area and open up new avenues that may aid in the treatment of inflammatory diseases.

The chemokine receptor CCR5 genetic polymorphism and expression in rheumatoid arthritis patients

OBJECTIVES

To identify the genetic polymorphism of the chemokine receptor CCR5 (the Delta32 allelic variant) in patients with rheumatoid arthritis (RA) and compare the findings with healthy controls. To compare the CCR5 phenotypic expression in T cells and monocytes isolated from the peripheral blood and synovial fluid in a subgroup of RA patients.

METHODS

CCR5 genes of 92 RA patients and 160 healthy controls were genotyped using specific primers flanking the region of deletion. The ethnic distribution was similar between the groups. Flow cytometric analysis was used for immunophenotyping the T cells and monocytes isolated from the peripheral blood and synovial fluid of eight RA patients. The isolated cells were triple stained with CD4 or CD8, CD25 and CCR5 monoclonal antibodies.

RESULTS

There was no difference in the CCR5Delta32 genotypic frequency between the RA patients and the control group (0.055 and 0.063, respectively, p = 0.989). No homozygote for the CCR5Delta32 allele was seen in either group. Five heterozygotes were identified in the RA patient group, whose disease was shown to be aggressive. A significant enrichment of activated CCR5+ monocytes was seen in the synovial fluid of the RA patients subjected to arthrocentesis, who were all homozygotes for the CCR5 wild-type genotype.

CONCLUSION

A protective role for the CCR5 allelic variant in RA development was not observed. Disease severity in the heterozygotes suggests that other proinflammatory mechanisms might overcome this mutation in vivo. The activated CCR5+ monocyte enrichment in the rheumatoid synovial fluid might indicate that this cell population has an important role in the pathogenesis of the disease.