The gene encoding CD23 leukocyte antigen (FCE2) is located on human chromosome 19

Serum Fcεrii Receptor (SCD23) as an Evaluating Factor for Grass Pollen Immunotherapy

CD23 is a protein on the surface of certain hemopoietic cells and it is considered to be the low affinity receptor for immunoglobulin IgE, (FcεRll/CD23). The regulation of the expression of CD23 depends on the type of cell on which it is found. Like most of the FcR receptors, it is released in a soluble form (sCD23) in the extracellular fluid. This form is found in increased levels in the serum of allergic patients and in neoplastic diseases. We studied total IgE and sCD23 in the serum of 30 allergic patients undergoing immunotherapy, 15 allergic patients treated only symptomatically for grass pollen (GP) allergy, 15 healthy and subjects. We found that the mean values of total IgE and sCD23 after the course of hyposensitization were decreased compared to those before treatment as well as to those GP allergic patients under conventional therapy and to healthy adults. However, only the CD23 decrease was statistically significant. Therefore, we speculate that determination of sCD23 may be useful for (a) the general evaluation of allergic patients and (b) the immunological monitoring of patients under immunotherapy.

Genetic variations of the FCER2 gene and asthma susceptibility in north Indian children: a case-control study

CONTEXT AND OBJECTIVE

The findings showed that the low-affinity IgE receptor plays a pivotal role in allergic immune response and it is a pharmacogenetic predictor in asthma disease. This study aims to investigate the association of genetic variations: rs28364072 and rs7249320 with asthma and its severity in north Indian children.

METHODS

Case-control-based genetic association study was performed among 550 children.

RESULTS

Statistical analysis demonstrated significant association between asthma and genotypes frequency of both the SNPs.

CONCLUSIONS

Our data indicate that the studied variations are strongly associated with asthma susceptibility and might be risk factor among north Indian asthmatic children.

CD23/FcεRII: molecular multi-tasking

CD23 is the low-affinity receptor for immunoglobulin (Ig)E and plays important roles in the regulation of IgE responses. CD23 can be cleaved from cell surfaces to yield a range of soluble CD23 (sCD23) proteins that have pleiotropic cytokine-like activities. The regions of CD23 responsible for interaction with many of its known ligands, including IgE, CD21, major histocompatibility complex (MHC) class II and integrins, have been identified and help to explain the structure-function relationships within the CD23 protein. Translational studies of CD23 underline its credibility as a target for therapeutic intervention strategies and illustrate its involvement in mediating therapeutic effects of antibodies directed at other targets.

Regulation of CD23 expression by Notch2 in B-cell chronic lymphocytic leukemia

The original observation that sera from patients with chronic B-cell lymphocytic leukemia (B-CLL) contain high amounts of soluble CD23 (sCD23), which reflect disease activity and tumor load has been confirmed by numerous reports and serial determinations of sCD23 are now recognized as important indicators of disease progression. The reason why the leukemic cells over express CD23 and subsequently release large quantities of sCD23 as compared to healthy persons or patients with other lymphoproliferative disorders is still not clear. However, progress has been made in understanding the mechanism leading to the upregulation of CD23 in the leukemic cells. Following is an update on clinical data and a short review on the potential functions of CD23 as well as its regulation by Notch2 in B-CLL.

Constitutional polymorphisms of prostate cancer: prognostic and diagnostic implications

Prostate cancer is the most common cancer diagnosis in men. While often perceived as a slow, indolent malignancy, prostate cancer trails only lung cancer among cancer-related mortality in men. Current diagnosis and treatment algorithms are plagued by overdiagnosis of non-lethal indolent prostate cancer with no proven means to predict, detect, and prevent aggressive lethal prostate cancer in men most at risk. These challenges are particularly concerning for African-American men who demonstrate increased rates of prostate cancer incidence and mortality when compared to other ethnic groups. With the completion of the human genome project, technology and techniques now exist to differentiate cancer from normal tissues based on the expression patterns of thousands of genes assessed simultaneously on a single microarray gene 'chip'. This platform has greatly improved our understanding of genes that regulate tumor behavior once cancer is established. Microarrays can also be utilized in patients without cancer to determine which patients are at high risk for tumor development and in need of rational prevention strategies. Constitutional single nucleotide polymorphisms (SNPs) are one source of genetic variation and may serve as a means to identify these high-risk individuals. SNPs are single nucleotide base pair changes within a gene which occur in one percent or more of the population. SNPs can contribute to a disease state by altering the function of a protein encoded by a gene without affecting gene expression. This review will examine the current understanding of constitutional SNPs associated with prostate cancer carcinogenesis, highlight two current diagnostic array platforms and discuss implications for future prevention and screening programs.

Anti-CD23

CD23, the low-affinity immunoglobulin (Ig)E receptor (FcepsilonRII), is widely distributed on the surface of various human cells. CD23 mediates numerous IgE-related immune responses (including allergen focusing) by enhancing IgE antigen complex presentation, regulating IgE synthesis, influencing cell differentiation and growth of both B- and T-cells, and stimulating production of pro-inflammatory mediators from monocytes/macrophages, eosinophils, and even airway smooth muscle cells. Both membrane and soluble CD23 play an important role in allergic reactions. Cellular contacts and cytokines modulate its expression in a concerted manner as needed for allergic reactions. Expression of CD23 and soluble CD23 has been associated with allergic diseases. Targeting CD23 with monoclonal antibody (MAb) is a promising candidate therapy in allergic diseases. A newly developed agent known as Lumiliximab, which is an anti-CD23 MAb (Lumiliximab), was demonstrated to be a well-tolerated agent in a phase I clinical trial (a placebo-controlled study with allergic asthma). Adverse events were mild, and no relationship was apparent between the dose of Lumilixilab and the frequency, severity, or type of event. Sustained and dose-dependent decreases in mean serum total IgE concentrations were noted. The serum half-life of Lumilixilab increased from 2 to 10 d with increasing doses. Blocking antigen presentation, preventing costimulation signals, and reducing production of pro-inflammatory mediators are some of the potential mechanisms involved for anti-CD23 activity. Although the safety and clinical efficacy of Lumilixilab in allergic asthma and rhinitis require confirmation, the observed data imply that anti-CD23 is a promising candidate therapy option for future treatment of allergic diseases.

Association study of the chromosomal region containing the FCER2 gene suggests it has a regulatory role in atopic disorders

On the basis of studies with animal models, the gene for the low-affinity receptor for immunoglobulin E (IgE) (FCER2, CD23) has been implicated as a candidate for IgE-mediated allergic diseases and bronchial hyperreactivity, or related traits. Given evidence for genetic complexity in atopic disorders, we sought to study two European subpopulations, Finnish and Catalonian. We studied three phenotypic markers: (1) total serum IgE level; (2) asthma; and (3) specific IgE level for a mixture of the most common aeroallergens in Finland. Altogether, eight polymorphic markers spanning a region of 10 cM around the FCER2 gene on chromosome 19p13 were analyzed in 124 families. The physical order of the markers and the location of the FCER2 gene were confirmed by using radiation hybrids. The allele and haplotype association study showed a suggestive haplotype association (significance of p </= 0.03 based on a permutation test) for a high serum IgE response. In a subset of chromosomes segregating with asthma in families with two or more affected members, a single haplotype was found to be highly enriched (p = 8.3 x 10(-6)). However, sequence polymorphisms, which would verify structural differences in the FCER2 gene, were not detected in the coding region of the receptor. Our results suggest that chromosome 19p13 might harbor a genetic determinant of IgE-related traits. Studies in other population samples are needed to verify this finding.

Structure and functions of CD23

This review summarizes recent data on CD23, a low affinity receptor for IgE (Fc epsilon RII). CD23 is the only FcR which does not belong to the immunoglobulin gene superfamily. The CD23 molecule was discovered independently as an IgE receptor on human lymphoblastoid B cells [1], as a cell surface marker expressed on Epstein-Barr-Virus-transformed B cells (EBVCS) [2] and as a B-cell activation antigen (Blast 2) [3]. CD23 was shown to be a low affinity receptor for IgE [4,5]. Similar to most FcR, soluble forms of CD23 (sCD23) are released into extracellular fluids. The soluble fragments formed by proteolytic cleavage of surface CD23 are not only capable of binding IgE (IgE binding factors) but also exhibit multiple functions that are not IgE related. These observations together with the finding that CD23 displays significant homology with Ca(2+)-dependent (C-type) animal lectins, suggested the existence of natural ligands other than IgE. The recent finding that CD23 interacts with CD21, CD11b and CD11c indicates that CD23 should be viewed not only as a low affinity IgE receptor but also as an adhesion molecule involved in cell-cell interaction. After a brief overview of the molecular structure, there follows a discussion of the biological activities ascribed to human CD23.

A novel interleukin-12 p40-related protein induced by latent Epstein-Barr virus infection in B lymphocytes

We have isolated a cDNA encoding a novel hematopoietin receptor family member related to the p40 subunit of interleukin-12 and to the ciliary neurotrophic factor receptor, whose expression is induced in B lymphocytes by Epstein-Barr virus (EBV) infection. This gene, which we have designated EBV-induced gene 3 (EBI3), encodes a 34-kDa glycoprotein which lacks a membrane-anchoring motif and is secreted. Despite the absence of a membrane-anchoring motif and of cysteines likely to mediate covalent linkage to an integral membrane protein, EBI3 is also present on the plasma membrane of EBV-transformed B lymphocytes and of transfected cells. Most newly synthesized EBI3 is retained in the endoplasmic reticulum in an endoglycosidase H-sensitive form associated with the molecular chaperone calnexin and with a novel 60-kDa protein. EBI3 is expressed in vivo by scattered cells in interfollicular zones of tonsil tissue, by cells associated with sinusoids in perifollicular areas of spleen tissue, and at very high levels by placental syncytiotrophoblasts. EBI3 expression in vitro is induced in EBV-negative cell lines by expression of the EBV latent infection membrane protein-1 and in peripheral blood mononuclear cells by pokeweed mitogen stimulation. EBI3 maps to chromosome 19p13.2/3, near genes encoding the erythropoietin receptor and the cytokine receptor-associated kinase, Tyk2. EBI3 synthesis by trophoblasts and by EBV-transformed cells and similarities to interleukin-12 p40 are compatible with a role for EBI3 in regulating cell-mediated immune responses.

Chromosomal location and isoform analysis of mouse Fc epsilon RII/CD23

The gene for the mouse low affinity receptor for IgE (Fc epsilon RII, also known as CD23) was mapped on Chromosome (Chr) 8 proximal to Plat. This gene, symbolized Fcer2 (formerly Fce2) resides in a region of Chr 8 with linkage homology with human chromosomes 8 and 19. The mouse Fc epsilon RII was examined for the presence of alternate N-terminal forms such as seen in humans. An antisense RNA probe was prepared from the 5' end of the cDNA through the first 660 bp of the cDNA and was used to analyze message from Fc epsilon RII+ B cells and B cell hybridomas both before and after treatment with interleukin 4 (IL-4). Using RNase protection analysis, a major 640 bp band corresponding to the full length probe was seen, even after activation of the cells with LPS in the presence of IL-4, which is known to give high expression levels of the Fc epsilon RII. This result suggests that the mouse does not produce significant levels of an alternate IL-4 inducible Fc epsilon RII, as seen in man, and this may explain the more restricted cell lineage expression of the Fc epsilon RII in the mouse.

Chromosomal localization in man and rat of the genes encoding the liver-enriched transcription factors C/EBP, DBP, and HNF1/LFB-1 (CEBP, DBP, and transcription factor 1, TCF1, respectively) and of the hepatocyte growth factor/scatter factor gene (HGF)

By means of somatic cell hybrids segregating either human or rat chromosomes, we determined the chromosome localization of three genes encoding transcription factors expressed in hepatocytes, namely, C/EBP (CCAAT/enhancer binding protein), DBP (D site of albumin promoter binding protein), and HNF1/LFB-1 (designated transcription factor 1, gene symbol: TCF1), and of the hepatocyte growth factor gene, which is identical to the mitogenic and chemotactic factor designated scatter factor (gene symbol:HGF). The CEBP and DBP genes, encoding two related transcription factors, were found to be syntenic both on human chromosome 19 and on rat chromosome 1. These results provide further evidence for conservation of synteny on these two chromosomes (and on mouse chromosome 7). The TCF1 gene was found to be located on chromosome 12 in both man and rat, thereby defining a new segment of homology between these two species (and a segment of mouse chromosome 5). The HGF gene was mapped to rat chromosome 4, confirming homology between this chromosome and human chromosome 7, which carries the human HGF gene.

The Sp1 transcription factor gene (SP1) and the 1,25-dihydroxyvitamin D3 receptor gene (VDR) are colocalized on human chromosome arm 12q and rat chromosome 7

By means of somatic cell hybrids segregating either human or rat chromosomes, the genes encoding the transcription factor Sp1 (SP1) and the 1,25-dihydroxyvitamin D3 receptor (VDR) were both assigned to human chromosome arm 12q and to rat chromosome 7. This result implies that the locus for the clinical disorder vitamin D dependency rickets type II maps on 12q. The phenylalanine hydroxylase (PAH) and the retinoic acid receptor-gamma (RARG) genes also map on human chromosome arm 12q and rat chromosome 7, indicating that a synteny group is conserved on these chromosomes.

The Interleukin-6-dependent DNA-binding protein gene (transcription factor 5: TCF5) maps to human chromosome 20 and rat chromosome 3, the IL6 receptor locus (IL6R) to human chromosome 1 and rat chromosome 2, and the rat IL6 gene to rat chromosome 4

Using two panels of somatic cell hybrids segregating either human or rat chromosomes, the gene encoding the interleukin-6-dependent DNA-binding protein, also called liver activator protein (designated transcription factor 5: TCF5), was assigned to human chromosome 20 and to rat chromosome 3. The TCF5 gene might be identical with the NF-IL6 gene. The locus encoding the IL6 receptor gene (IL6R) was localized to human chromosome 1 and rat chromosome 2. An IL6R-like (IL6RL) locus was also assigned to human chromosome 9. In addition, the rat interleukin-6 (IL6) gene was assigned to rat chromosome 4. These mapping data allow one to extend comparison between the rat, mouse, and human gene maps.