The FCRL3-169CT promoter single-nucleotide polymorphism, which is associated with systemic lupus erythematosus in a Japanese population, predicts expression of receptor protein on CD19+ B cells

Upregulated Fcrl5 disrupts B cell anergy and causes autoimmune disease

B cell anergy plays a critical role in maintaining self-tolerance by inhibiting autoreactive B cell activation to prevent autoimmune diseases. Here, we demonstrated that Fc receptor-like 5 (Fcrl5) upregulation contributes to autoimmune disease pathogenesis by disrupting B cell anergy. Fcrl5-a gene whose homologs are associated with human autoimmune diseases-is highly expressed in age/autoimmunity-associated B cells (ABCs), an autoreactive B cell subset. By generating B cell-specific Fcrl5 transgenic mice, we demonstrated that Fcrl5 overexpression in B cells caused systemic autoimmunity with age. Additionally, Fcrl5 upregulation in B cells exacerbated the systemic lupus erythematosus-like disease model. Furthermore, an increase in Fcrl5 expression broke B cell anergy and facilitated toll-like receptor signaling. Thus, Fcrl5 is a potential regulator of B cell-mediated autoimmunity by regulating B cell anergy. This study provides important insights into the role of Fcrl5 in breaking B cell anergy and its effect on the pathogenesis of autoimmune diseases.

Lymphocytes sense antibodies through human FCRL proteins: Emerging roles in mucosal immunity

Members of the Fc receptor-like (FCRL) family modulate B and T cell responses, yet their functional roles remain enigmatic. Nevertheless, FCRL3 promoter polymorphism that alters gene expression has been associated with autoimmune disease risk, indicating physiologic importance. Providing essential functional context, human FCRL3, FCRL4, and FCRL5 have recently been identified as secretory IgA (SIgA), dimeric IgA, and IgG receptors, respectively, revealing novel ways lymphocytes can interact with antibodies. FCRL3 and FCRL4 are able to distinguish the mucosal and systemic origin of IgA-containing immune complexes, respectively, with clear implications in guiding mucosal responses. SIgA can signal mucosal breach through FCRL3, driving the functional plasticity of regulatory T cells toward inflammatory to help control invading pathogens. Conversely, recognition of dimeric IgA by FCRL4 on memory B cells located in mucosa-associated lymphoid tissues could promote tolerance to commensals. Memory B cells that accumulate under conditions of chronic antigen presence frequently express FCRL4 and FCRL5, and antibody ligands could provide functional feedback to the cells. FCRL5 apparently recognizes the age of the IgG molecule, using deamidation as a molecular clock, conceivably playing regulatory roles in chronic antibody responses. A framework of FCRL3, FCRL4, and FCRL5 operating as sensors of antibodies in immune complexes is proposed. Sensing the spatial origin and age of immune complexes can shape lymphocyte functional attributes and inform their participation in mucosal immune responses. The potential contributions of FCRL3 and SIgA to the pathogenesis of autoimmune diseases are discussed.

Evolution of Fc Receptor-Like Scavenger in Mammals

Fc receptor-like (FCRL) molecules comprise a large family of receptors, homologous to the receptors for the Fc portion of immunoglobulins (FCR). Within this family, an unusual gene known to exist in mice, rats and dogs, termed FCRLS, encodes a chimeric protein with both Ig-like FCRL and type B scavenger-receptor cysteine-rich (SRCR)-like domains. In mice, FCRLS is located next to the CD5L and KIRREL1 genes. Here, we show that the curious FCRLS gene is actually present across major mammalian groups, but its annotation is generally incorrect or absent. Anchored on mouse FCRLS and FCRL2 genomic sequence alignments, phylogenetic analyses demonstrated that many mammalian sequences currently annotated as FCRL2 cluster with FCRLS, supported by a conserved genetic synteny among organisms. This analysis shows that FCRLS is present in Rodentia, some Carnivora (Canidae and Ursidae), Chiroptera, Arctiodactyla, Proboscidae, and some Primata. Thus, the FCRLS most likely originated in a eutherian mammal ancestor since it is not present in Monotremata or Marsupialia. FCRLS has a peculiar distribution pattern across mammalian lineages, being present in some species, but absent in others from the same family, as in carnivores for example. The most parsimonious hypothesis to explain this FCRLS evolution is that it was convergently lost in several independent mammalian lineages. Analyses of branch-specific nucleotide evolutionary rates, show that FCRL2 and FCRLS have similar ranges of rates across mammals, suggesting that both genes have crucial, but separate functions in the immune system. Bayesian estimates of evolutionary rates for FCRLS in mammalian lineages revealed that carnivores display the highest mutation rate after rodents. Additionally, positive diversifying selection was detected for both FCRL2 and FCRLS. Our results show that the presence of the FCRLS gene is older and more widespread across mammals than previously thought and appears to be functional, being under positive selection. Its precise physiologic role should thus be investigated.

Two genetic variants explain the association of European ancestry with multiple sclerosis risk in African-Americans

Epidemiological studies have suggested differences in the rate of multiple sclerosis (MS) in individuals of European ancestry compared to African ancestry, motivating genetic scans to identify variants that could contribute to such patterns. In a whole-genome scan in 899 African-American cases and 1155 African-American controls, we confirm that African-Americans who inherit segments of the genome of European ancestry at a chromosome 1 locus are at increased risk for MS [logarithm of odds (LOD) = 9.8], although the signal weakens when adding an additional 406 cases, reflecting heterogeneity in the two sets of cases [logarithm of odds (LOD) = 2.7]. The association in the 899 individuals can be fully explained by two variants previously associated with MS in European ancestry individuals. These variants tag a MS susceptibility haplotype associated with decreased CD58 gene expression (odds ratio of 1.37; frequency of 84% in Europeans and 22% in West Africans for the tagging variant) as well as another haplotype near the FCRL3 gene (odds ratio of 1.07; frequency of 49% in Europeans and 8% in West Africans). Controlling for all other genetic and environmental factors, the two variants predict a 1.44-fold higher rate of MS in European-Americans compared to African-Americans.

FCRL3 promotes IL-10 expression in B cells through the SHP-1 and p38 MAPK signaling pathways

Multiple sclerosis (MS) is an autoimmune disease of the central nervous system that is caused by the interaction of genetic and environmental factors. Current studies have shown that Fc-receptor like-3 (FCRL3) is closely related to MS, but the specific role of FCRL3 in MS has not yet been clarified. This study further found that FCRL3 and interleukin 10 (IL-10) expression was downregulated in MS patients, but the expression of these proteins was higher in the remission phase than that in the acute phase. The C allele of rs7528684 was associated with MS, and the CC genotype could lead to the upregulation of FCRL3 expression and the increase in IL-10 secretion. Further in vitro experiments with B cells found that lipopolysaccharide (LPS) promoted FCRL3 expression in a dose- and time-dependent manner, thereby promoting IL-10 secretion. LPS regulated Src homology region 2 domain-containing phosphatase-1 (SHP-1) expression and p38 mitogen-activated protein kinase (MAPK) pathway activation through FCRL3, and FCRL3 upregulated the SHP-1 expression and p38 phosphorylation levels. When SHP-1 small interfering RNA or a p38 pathway inhibitor was added, the effect of FCRL3 on IL-10 secretion was significantly inhibited. In addition, FCRL3 inhibited the secretion of inflammatory factors (tumor necrosis factor-α, IL-1β, IL-6, and IL-8); after inhibiting the expression of IL-10, the abovementioned effects of FCRL3 were blocked. These results suggest that FCRL3 can activate the SHP-1 and p38 MAPK pathways and then promote the secretion of IL-10 in B cells, thus inhibiting the secretion of inflammatory factors. Therefore, FCRL3 may play an immunoprotective role in MS, and it will be an effective target for the diagnosis and treatment of MS.

Anti-Apolipoprotein A-1 IgG Predict All-Cause Mortality and Are Associated with Fc Receptor-Like 3 Polymorphisms

Background

Autoantibodies against apolipoprotein A-1 (anti-apoA-1 IgG) have emerged as an independent biomarker for cardiovascular disease and mortality. However, their association with all-cause mortality in the community, as well as their genetic determinants, have not been studied.

Objective

To determine whether anti-apoA-1 IgG: (a) predict all-cause mortality in the general population and (b) are associated with single-nucleotide polymorphisms (SNPs) in a genome-wide association study (GWAS).

Methods

Clinical, biological, and genetic data were obtained from the population-based, prospective CoLaus study, including 5,220 participants (mean age 52.6 years, 47.3% men) followed over a median duration of 5.6 years. The primary study outcome was all-cause mortality.

Results

After multivariate adjustment, anti-apoA-1 IgG positivity independently predicted all-cause mortality: hazard ratio (HR) = 1.54, 95% confidence interval (95% CI): 1.11–2.13, P = 0.01. A dose–effect relationship was also observed, each SD of logarithmically transformed anti-apoA-1 IgG being associated with a 15% increase in mortality risk: HR = 1.15, 95% CI: 1.02–1.28, P = 0.028. The GWAS yielded nine SNPs belonging to the Fc receptor-like 3 (FCRL3) gene, which were significantly associated with anti-apoA-1 IgG levels, with the lead SNP (rs6427397, P = 1.54 × 10⁻⁹) explaining 0.67% of anti-apoA-1 IgG level variation.

Conclusion

Anti-apoA-1 IgG levels (a) independently predict all-cause mortality in the general population and (b) are linked to FCRL3, a susceptibility gene for numerous autoimmune diseases. Our findings indicate that preclinical autoimmunity to anti-apoA-1 IgG may represent a novel mortality risk factor.

Human FcR polymorphism and disease

Fc receptors play a central role in maintaining the homeostatic balance in the immune system. Our knowledge of the structure and function of these receptors and their naturally occurring polymorphisms, including single nucleotide polymorphisms and/or copy number variations, continues to expand. Through studies of their impact on human biology and clinical phenotype, the contributions of these variants to the pathogenesis, progression, and/or treatment outcome of many diseases that involve immunoglobulin have become evident. They affect susceptibility to bacterial and viral pathogens, constitute as risk factors for IgG or IgE mediated inflammatory diseases, and impact the development of many autoimmune conditions. In this chapter, we will provide an overview of these genetic variations in classical FcγRs, FcRLs, and other Fc receptors, as well as challenges in achieving an accurate and comprehensive understanding of the FcR polymorphisms and genomic architecture.

Emerging roles for the FCRL family members in lymphocyte biology and disease

Members of the extended Fc receptor-like (FCRL) family in humans and mice are preferentially expressed by B cells and possess tyrosine-based immunoregulatory function. Although the majority of these proteins repress B cell receptor-mediated activation, there is an emerging evidence for their bifunctionality and capacity to counter-regulate adaptive and innate signaling pathways. In light of these findings, the recent discovery of ligands for several of these molecules has begun to reveal exciting potential for them in normal lymphocyte biology and is launching a new phase of FCRL investigation. Importantly, these fundamental developments are also setting the stage for defining their altered roles in the pathogenesis of a growing number of immune-mediated diseases. Here we review recent advances in the FCRL field and highlight the significance of these intriguing receptors in normal and perturbed immunobiology.

The FCRL3 -169T>C polymorphism and the risk of endometriosis-related infertility in a Polish population

OBJECTIVE

Recently, the FCRL3 -169T>C (rs7528684) single-nucleotide polymorphism (SNP) has been demonstrated to be a risk factor of endometriosis related infertility. We studied whether the FCRL -169T>C SNP can be associated with endometriosis-related infertility in a sample of the Polish population

METHODS

Using PCR-RFLP analysis we genotyped 141 infertile women with endometriosis and 519 fertile women. FCRL3 transcript levels were determined by reverse transcription and real-time quantitative PCR analysis in CD19(+) B cells from women with endometriosis-associated infertility and fertile women

RESULTS

We found a significantly increased frequency of the FCRL3 C/C genotype in women with endometriosis-associated infertility than controls [OR = 1.681 (95 % CI = 1.120-2.522, p = 0.0116, p corr = 0.0348)]. There was also a statistically increased frequency of the C/C and C/T genotypes in patients compared with controls [OR = 2.009 (95 % CI = 1.214-3.324, p = 0.0059, p corr = 0.0177)]. The p value of the χ (2) test for the trend observed for the FCRL3 -169T>C polymorphism was also statistically significant (p trend = 0.0012, p corr = 0.0036). We also found significantly increased FCRL3 transcript levels in carriers of the FCRL3 -169 CC vs TT and CT vs TT genotype both in women with endometriosis-related infertility (p = 0.012; p = 0.015) and fertile women (p = 0.017; p = 0.032) CONCLUSIONS: FCRL3 -169T>C polymorphism alters the expression of FCRL3 and can be a risk factor of endometriosis-related infertility.

FCRL3 promotes TLR9-induced B-cell activation and suppresses plasma cell differentiation

Fc receptor-like (FCRL) molecules are preferentially expressed by B lymphocytes and possess tyrosine-based immunoregulatory function. Although they generally inhibit B-cell receptor signaling, their influence on other activation pathways remains largely unexplored. In humans, FCRL3 encodes a type I transmembrane protein harboring both cytoplasmic ITAM and ITIM elements that can repress B-cell receptor activation. Despite this inhibitory property, mounting associations for FCRL3 with autoimmune and lympho-proliferative disorders imply a role for it in promoting B-cell pathogenesis. Here, we explore the influence of FCRL3 on B-cell responses to innate TLR9 stimulation. A detailed survey of blood B-cell populations found that FCRL3 expression increased as a function of differentiation and was higher among memory subsets with innate-like features. FCRL3 ligation augmented CpG oligodeoxynucleotide TLR9-mediated B-cell proliferation, activation, and survival, but surprisingly, abrogated plasma cell differentiation and antibody production. Although FCRL3 amplified the NF-κB and mitogen-activated protein kinase signaling cascades, it halted CpG triggered BLIMP1 induction in an ERK-dependent fashion. These findings indicate that FCRL3 differentially modulates innate signaling in B cells and provide new insight into the potential of this disease-associated receptor to counter-regulate adaptive and innate immunity.

The FCRL3 -169T>C polymorphism might be associated with some autoantibody presence in patients with SLE in a Polish population

OBJECTIVES: The Fcrl3 -169T>C (rs7528684) polymorphism has been shown to be a risk factor of various autoimmune diseases, including systemic lupus erythematosus (SLE); however, these results are inconsistent between distinct ethnicities. METHODS: Using PCR-RFLP we studied the distribution of the FCRL3 -169T>C polymorphism in SLE patients (n = 263) and controls (n = 528) in a sample from the Polish population. RESULTS: We found no significant differences of FCRL3 -169T>C genotypes and alleles between patients with SLE and healthy individuals. However, in the dominant model we found a significant association between the FCRL3 -169T>C polymorphism and the presence of anti-Scl-70 antibody (Ab) [OR = 4.747 (95 % CI = 1.639-13.749), p = 0.0011, p corr = 0.0198]. Moreover, in the dominant model we observed a significant contribution of FCRL3 -169T>C to the presence of either anti-La or anti-Scl-70 Abs [OR = 4.378 (95 % CI = 1.793-10.690, p = 0.0003, p corr = 0.0054)]. CONCLUSIONS: Our study demonstrated that the FCRL3 -169T>C polymorphism is not a risk factor of SLE in the Polish population, but this polymorphism may contribute to autoantibody production in this disease.

Fc receptor-like 3 (FCRL3) -169 C/T polymorphism and systemic lupus erythematosus: a meta-analysis

Our aim was to determine whether the Fc receptor-like 3 (FCRL3) -169 C/T (rs7528684) polymorphism confers susceptibility to systemic lupus erythematosus (SLE). A meta-analysis was conducted on the associations between the FCRL3 -169 C/T polymorphism and the SLE. A total of nine sets of comparisons containing 3,628 patients and 6,490 controls were considered. The meta-analysis showed no association between the SLE and the FCRL3 -169 C allele in all study patients (odds ratio [OR] = 0.999, 95 % confidence interval [CI] = 0.925-1.080, p = 0.986). Stratification by ethnicity indicated no association between the C allele and the SLE in neither Europeans nor Asians (OR = 1.058, 95 % CI = 0.925-1.250, p = 0.414; OR = 0.981, 95 % CI = 0.884-1.088, p = 0.715). Furthermore, analysis using the recessive model, the dominant model, and the homozygote contrast showed the same pattern for the C allele in European and Asian groups, showing no association between the FCRL3 -169 C/T polymorphism and the SLE. Even after excluding studies whose controls were not in Hardy-Weinberg equilibrium, we found that this did not materially affect the meta-analysis results. However, the single Latin American study did show an association between the FCRL3 polymorphism and the SLE under homozygote contrast (OR for CC vs. TT = 2.689, 95 % CI = 1.152-1.277, p = 0.022). This meta-analysis of published studies including 2,544 patients and 3,913 controls demonstrates that the FCRL3 -169 C/T polymorphism does not confer susceptibility to SLE in Europeans or Asians.

A functional variant in FCRL3 is associated with higher Fc receptor-like 3 expression on T cell subsets and rheumatoid arthritis disease activity

OBJECTIVE

CD4+FoxP3+ Treg cells suppress effector T cells and prevent autoimmune disease. Treg cell function is deficient in active rheumatoid arthritis (RA), a loss which may play a role in the pathogenesis of this disease. We previously showed that a single-nucleotide polymorphism in the FCRL3 gene led to higher expression of Fc receptor-like 3 (FcRL3) on Treg cells and that FcRL3+ Treg cells are functionally deficient in comparison to FcRL3- Treg cells. This study was undertaken to investigate the potential role of FcRL3 in RA.

METHODS

A cross-sectional study was performed to evaluate the FCRL3 -169 genotype and FcRL3 expression on T cell subsets, including Treg cells, in peripheral blood samples from 51 patients with RA enrolled in the University of California, San Francisco (UCSF) RA Cohort. Clinical data were obtained from the UCSF RA Cohort database.

RESULTS

Patients with the FCRL3 -169C allele (genotype C/C or C/T) expressed higher levels of FcRL3 on Treg cells, and on CD8+ and γ/δ T cells, in comparison to RA patients with the T/T genotype. Higher FcRL3 expression on these T cell subpopulations correlated with RA disease activity in patients harboring the FCRL3 -169C allele. Furthermore, FcRL3 expression on Treg cells was higher in patients with erosive RA, and the FCRL3 -169C allele was overrepresented in patients with erosive RA.

CONCLUSION

Our findings indicate that FcRL3 expression, which is strongly associated with the presence of the FCRL3 -169C allele, may serve as a biomarker for RA disease activity.

FCRL3 -169C/C genotype is associated with anti-citrullinated protein antibody-positive rheumatoid arthritis and with radiographic progression

OBJECTIVE

Studies of Caucasian populations have shown conflicting results concerning the association between a promoter polymorphism -169T>C of the Fc receptor-like 3 (FCRL3) gene and rheumatoid arthritis (RA). It is unknown whether FCRL3 is associated with autoantibody status and disease severity. We investigated associations between FCRL3 -169T>C and autoantibody status and joint damage in patients with RA.

METHODS

A total of 652 Norwegian patients with RA from 2 cohorts and 981 Norwegian controls, previously genotyped for FCRL3 -169T>C (rs7528684), were studied. Data on anticitrullinated protein antibodies (ACPA) and rheumatoid factor (RF) were available. The EURIDISS cohort (disease duration ≤ 4 yrs at baseline) was followed longitudinally, with assessment of radiographic hand damage at baseline and after 10 years (n = 117) according to the van der Heijde-modified Sharp score.

RESULTS

We found significant associations with ACPA-positive RA for both the C allele (OR 1.28, 95% CI 1.08-1.52, p = 0.004) and the C/C genotype (OR 1.57, 95% CI 1.18-2.10, p = 0.002). Similar associations were seen with RF-positive RA. No association was found with ACPA-negative or RF-negative RA. The C/C genotype was found to be associated with 10-year radiographic progression in multivariate linear and logistic regression analyses, after adjustment for ACPA, erythrocyte sedimentation rate, age, and sex.

CONCLUSION

The promoter polymorphism of FCRL3 was associated with autoantibody-positive RA. Despite the low number of patients, the C/C genotype of the FCRL3 polymorphism consistently and independently predicted radiographic progression. These findings suggest that FCRL3 is involved in both disease susceptibility and progression.

Genetic association of Fc receptor-like 3 polymorphisms with susceptibility to primary biliary cirrhosis: ethnic comparative study in Japanese and Italian patients

A functional variant in the Fc receptor-like 3 (FCRL3) gene is associated with the susceptibility to several autoimmune diseases. In this study, we examined whether the FCRL3 is associated with susceptibility to primary biliary cirrhosis (PBC) by comparing the two different ethnic groups, Japanese and Italians. We enrolled 232 patients with PBC and 230 controls in Japanese, and 216 PBC and 180 controls in Italians. Minor allele frequency of fcrl3_3 (-169 T>C) in the patients with PBC and controls was 0.20 and 0.09 in Japanese and 0.24 and 0.21 in Italians, respectively. We found a significant association of fcrl3_3 with PBC only in Japanese (P = 9.64 × 10(-7) ). These findings support the presence of common FCRL3-related pathological pathways in several autoimmune diseases, especially in Asians.

Disease Phenotypes and Gender Association of FCRL3 Single-Nucleotide Polymorphism −169T/C in Taiwanese Patients with Systemic Lupus Erythematosus and Rheumatoid Arthritis

Objective.

To investigate the association of the functional FCRL3 single-nucleotide polymorphism (SNP) −169T/C with disease phenotypes and susceptibility to systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA) in Taiwanese.

Methods.

FCRL3 SNP −169T/C was genotyped in 573 patients with SLE, 670 patients with RA, and 758 controls. Genotype distributions and allele frequencies were compared among the 3 groups as aggregates or as stratified by clinical characteristics, autoantibody profile, and sex within patient groups.

Results.

Overall, FCRL3 SNP −169T/C was not associated with susceptibility to either SLE or RA. However, −169CC genotype was significantly reduced in leukopenia-positive SLE patients as compared to the leukopenia-negative SLE patients (CC vs CT+TT, p = 6 × 10−4, OR 0.444, 95% CI 0.279–0.708) and controls (p = 6.1 × 10−3, OR 0.583, 95% CI 0.396–0.857). On the other hand, −169TT genotypes were significantly more numerous in RA patients with non-destructive disease as compared with patients with destructive disease (CC+CT vs TT: p = 0.007, OR 1.672, 95% CI 1.149–2.432). The −169T allele frequency was also significantly increased in non-destructive RA compared with patients with destructive disease (C vs T: p = 0.010, OR 1.423, 95% CI 1.089–1.859). FCRL3 SNP −169TT homozygous donors were significantly more numerous among female cyclic citrullinated peptide (CCP)-negative RA patients versus female CCP-positive RA patients (CC+CT vs TT: p = 0.019, OR 1.64, 95% CI 1.085–2.479).

Conclusion.

The functional FCRL3 SNP −169T/C appears to play important roles in the development of certain phenotypes such as SLE leukopenia and RA disease severity in Taiwanese patients with SLE and RA.

Expression of the autoimmune susceptibility gene FcRL3 on human regulatory T cells is associated with dysfunction and high levels of programmed cell death-1

CD4(+)FoxP3(+) regulatory T cells (T(reg)) play a critical role in maintaining self-tolerance and inhibiting autoimmune disease. Despite being a major focus of modern immunological investigation, many aspects of T(reg) biology remain unknown. In a screen for novel candidate genes involved in human T(reg) function, we detected the expression of an autoimmune susceptibility gene, FcRL3, in T(reg) but not in conventional CD4(+) T cells. FcRL3 is an orphan receptor of unknown function with structural homology to classical Fc receptors. Numerous genetic studies have demonstrated a link between a single nucleotide polymorphism in the FCRL3 promoter and both overexpression of FcRL3 and autoimmune diseases such as rheumatoid arthritis. Given the critical role of T(reg) in suppressing autoimmunity, we sought to ascertain how expression of FcRL3 relates to the phenotype, differentiation, and function of T(reg). We show in this study that FcRL3 is expressed on a population of thymically derived T(reg) that exhibits a memory phenotype and high levels of programmed cell death-1. Purified FcRL3(+) T(reg) are less responsive to antigenic stimulation in the presence of IL-2 than their FcRL3(-) counterparts, despite intact proximal and distal IL-2 signaling as determined by phosphorylation of Stat-5 and upregulation of Bcl2. In vitro suppression assays demonstrated that FcRL3(+) T(reg) have reduced capacity to suppress the proliferation of effector T cells. These data suggest that FcRL3 expression is associated with T(reg) dysfunction that may, in turn, contribute to the loss of self-tolerance and the development of autoimmunity.