Landscape of <i>immunoglobulin heavy chain gamma</i> gene class switch recombination in patients with adult T-cell leukemia–lymphoma

Not available.

Fcγ receptor activation mediates vascular inflammation and abdominal aortic aneurysm development

BACKGROUND

Abdominal aortic aneurysm (AAA), a degenerative vascular pathology characterized by permanent dilation of the aorta, is considered a chronic inflammatory disease involving innate/adaptive immunity. However, the functional role of antibody-dependent immune response against antigens present in the damaged vessel remains unresolved. We hypothesized that engagement of immunoglobulin G (IgG) Fc receptors (FcγR) by immune complexes (IC) in the aortic wall contributes to AAA development. We therefore evaluated FcγR expression in AAA lesions and analysed whether inhibition of FcγR signaling molecules (γ-chain and Syk kinase) influences AAA formation in mice.

METHODS

FcγR gene/protein expression was assessed in human and mouse AAA tissues. Experimental AAA was induced by aortic elastase perfusion in wild-type (WT) mice and γ-chain knockout (γKO) mice (devoid of activating FcγR) in combination with macrophage adoptive transfer or Syk inhibitor treatment. To verify the mechanisms of FcγR in vitro, vascular smooth muscle cells (VSMC) and macrophages were stimulated with IgG IC.

RESULTS

FcγR overexpression was detected in adventitia and media layers of human and mouse AAA. Elastase-perfused γKO mice exhibited a decrease in AAA incidence, aortic dilation, elastin degradation, and VSMC loss. This was associated with (1) reduced infiltrating leukocytes and immune deposits in AAA lesions, (2) inflammatory genes and metalloproteinases downregulation, (3) redox balance restoration, and (4) converse phenotype of anti-inflammatory macrophage M2 and contractile VSMC. Adoptive transfer of FcγR-expressing macrophages aggravated aneurysm in γKO mice. In vitro, FcγR deficiency attenuated inflammatory gene expression, oxidative stress, and phenotypic switch triggered by IC. Additionally, Syk inhibition prevented IC-mediated cell responses, reduced inflammation, and mitigated AAA formation.

CONCLUSION

Our findings provide insight into the role and mechanisms mediating IgG-FcγR-associated inflammation and aortic wall injury in AAA, which might represent therapeutic targets against AAA disease.

Characterization of human FcεRIα chain expression and gene copy number in humanized rat basophilic leukaemia (RBL) reporter cell lines

Several laboratories have created rat basophil leukemia (RBL) cell lines stably transfected with the human high affinity IgE receptor (FcεRI_H). More recently, humanized RBL cell lines saw the introduction of reporter genes such as luciferase (RS-ATL8) and DsRed (RBL NFAT-DsRed). These reporters are more sensitive than their parental non-reporter humanized RBL cell lines. However, no studies so far have addressed the levels of FcεRI_H surface expression on humanized RBL cell lines. This is a critical parameter, as it determines the ability of these cells to be efficiently sensitized with human IgE, hence it should affect the sensitivity of the cell assay–a critical parameter for any diagnostic application. Our purpose was to assess and compare the levels of expression of the transfected FcεRI_H chain in humanized RBL cell lines. We compared surface levels of FcεRIα_H by flow cytometry, using a fluorescently labelled monoclonal antibody (CRA-1/AER-37) and determined receptor numbers using calibration microspheres. FcεRIα_H copy numbers were assessed by qPCR, and the sequence verified. Transfection with FcεRIγ_H cDNA was assessed for its ability to increase FcεRIα_H expression in the NFAT-DsRed reporter. While both SX-38 and RS-ATL8 expressed about 500.000 receptors/cell, RBL 703–21 and NFAT-DsRed had approximately 10- to 30-fold lower FcεRIα_H expression, respectively. This was neither related to FcεRI_H gene copy numbers, nor to differences in steady state mRNA levels, as determined by qPCR and RT-qPCR, respectively. Instead, FcεRIα_H surface expression appeared to correlate with the co-expression of FcεRIγ_H. Stable transfection of NFAT-DsRed cells with pBJ1 neo-huFcεRI gamma, which constitutively expresses FcεRIγ_H, increased FcεRIα_H chain expression levels. Levels of FcεRIα_H surface expression vary greatly between humanized RBL reporter cell lines. This difference will affect the sensitivity of the reporter system when used for diagnostic purposes.

Molecular Pathology of Severe Combined Immunodeficiency in Mice, Horses, and Dogs

Severe combined immunodeficiency (SCID) is an inherited disorder of humans, mice, horses, and dogs, in which affected individuals are incapable of generating antigen-specific immune responses. It occurs when lymphocyte precursors fail to differentiate into mature lymphocytes because of mutations within recombinase-activating genes 1 and 2 or within the genes encoding deoxyribonucleic acid (DNA)-dependent protein kinase (DNA-PK). It also occurs when differentiated lymphocytes are incapable of completing signal transduction pathways because of defects in cell surface receptors for interleukins (IL). A spontaneous mutation in DNA-PKcs of BALB/c mice results in SCID, as do experimentally induced mutations in RAG1 and RAG2. SCID in horses results from a spontaneous mutation in DNA-PKcs. Two molecular mechanisms account for SCID in dogs. Jack Russell Terriers have a mutation within the DNA-PKcs gene, whereas Cardigan Welsh Corgi and Basset Hound have different defects in the gene encoding the γ chain that is common to the receptors for IL-2, −4, −7, −9, −15, and −21. The location of the mutation within target genes influences the spectrum of diseases observed in affected animals.

Development of human B cells and antibodies following human hematopoietic stem cell transplantation to Rag2(-/-)γc(-/-) mice

Humanized mice represent a valuable model system to study the development and functionality of the human immune system. In the RAG-hu mouse model highly immunodeficient Rag2(-/-)γc(-/-) mice are transplanted with human CD34(+) hematopoietic stem cells, resulting in human hematopoiesis and a predominant production of B and T lymphocytes. Human adaptive immune responses have been detected towards a variety of antigens in humanized mice but both cellular and humoral immune responses tend to be weak and sporadically detected. The underlying mechanisms for inconsistent responses are poorly understood. Here, we analyzed the kinetics of human B cell development and antibody production in RAG-hu mice to better understand the lack of effective antibody responses. We found that T cell levels in blood did not significantly change from 8 to 28 weeks post-engraftment, while B cells reached a peak at 14 weeks. Concentrations of 3 antibody classes (IgM, IgG, IgA) were found to be at levels about 0.1% or less of normal human levels, but human antibodies were still detected up to 32 weeks after engraftment. Human IgM was detected in 92.5% of animals while IgG and IgA were detected in about half of animals. We performed flow cytometric analysis of human B cells in bone marrow, spleen, and blood to examine the presence of precursor B cells, immature B cells, naïve B cells, and plasma B cells. We detected high levels of surface IgM(+) B cells (immature and naïve B cells) and low levels of plasma B cells in these organs, suggesting that B cells do not mature properly in this model. Low levels of human T cells in the spleen were observed, and we suggest that the lack of T cell help may explain poor B cell development and antibody responses. We conclude that human B cells that develop in humanized mice do not receive the signals necessary to undergo class-switching or to secrete antibody effectively, and we discuss strategies to potentially overcome these barriers.

T lymphocyte antigen 4-modified dendritic cell therapy for asthmatic mice guided by the CCR7 chemokine receptor

The CD80/CD86-CD28 axis is a critical pathway for immuno-corrective therapy, and the cytotoxic T lymphocyte antigen 4 (CTLA4) is a promising immunosuppressor targeting the CD80/CD86-CD28 axis; however, its use for asthma therapy needs further optimization. A human CTLA4 fused with the IgCγ Fc (CTLA4Ig) and mouse CC chemokine receptor type7 (CCR7) coding sequences were inserted into a recombinant adenovirus (rAdV) vector to generate rAdV-CTLA4Ig and rAdV-CCR7. The naive dendritic cells (DCs) were infected with these rAdVs to ensure CCR7 and CTLA4Ig expression. The therapeutic effects of modified DCs were evaluated. rAdV-CTLA4Ig and rAdV-CCR7 infected DCs improved all asthma symptoms. Inflammatory cell infiltration and cytokine analysis showed that rAdV-CTLA4Ig and rAdV-CCR7-modified DC therapy reduced the number of eosinophils and lymphocyte and neutrophil infiltration in the lung. Interestingly, assessment of the humoral immunity showed that the IL-4 and IFNγ levels of the rAdV-CTLA4Ig and rAdV-CCR7-modified DC-treated mice decreased significantly and did not reverse the Th1/Th2 balance. DCs expressing CCR7 displayed guidance ability for DC migration, primarily for DCs in the inflammatory lung. Additionally, the rAdVs caused an inflammatory response by inducing DC differentiation, inflammatory cell infiltration and changes in cytokines; however, mice transplanted with rAdV-green fluorescent protein (GFP)-infected DCs displayed no asthma manifestations. In conclusion, CTLA4Ig-modified DCs exhibited a therapeutic effect on asthma, and CCR7 may guide DC homing. The combination of these two molecules may be a model for precision-guided immunotherapy.

Activated T cells secrete an alternatively spliced form of common γ-chain that inhibits cytokine signaling and exacerbates inflammation

The common γ-chain (γc) plays a central role in signaling by IL-2 and other γc-dependent cytokines. Here we report that activated T cells produce an alternatively spliced form of γc mRNA that results in protein expression and secretion of the γc extracellular domain. The soluble form of γc (sγc) is present in serum and directly binds to IL-2Rβ and IL-7Rα proteins on T cells to inhibit cytokine signaling and promote inflammation. sγc suppressed IL-7 signaling to impair naive T cell survival during homeostasis and exacerbated Th17-cell-mediated inflammation by inhibiting IL-2 signaling upon T cell activation. Reciprocally, the severity of Th17-cell-mediated inflammatory diseases was markedly diminished in mice lacking sγc. Thus, sγc expression is a naturally occurring immunomodulator that regulates γc cytokine signaling and controls T cell activation and differentiation.

Correlation of immunoglobulin G expression and histological subtype and stage in breast cancer

INTRODUCTION

Recently, growing evidence indicates that immunoglobulins (Igs) are not only produced by mature B lymphocytes or plasma cells, but also by various normal cells types at immune privileged sites and neoplasm, including breast cancer. However, the association of breast cancer derived IgG with genesis and development of the disease has not yet been established.

METHODS

In this study we examined the expression of IgG in 186 breast cancers, 20 benign breast lesions and 30 normal breast tissues. Both immunohistochemistry with antibodies to Igκ (immunoglobulin G κ light chain) and Igγ (immunoglobulin G heavy chain) and in situ hybridization with an antisense probe to IgG1 heavy chain constant region gene were performed. Various clinicopathological features were also analyzed.

RESULTS

We found that IgG is specifically expressed in human breast cancer cells. Both infiltrating ductal carcinoma and infiltrating lobular carcinoma had significantly greater numbers of Igκ and Igγ positive cancer cells as compared with medullary carcinoma, carcinoma in situ, and benign lesions (all p<0.05). In addition, IgG expression was correlated with breast cancer histological subtypes (p<0.01) and AJCC stages (p<0.05), with more abundance of IgG expression in more malignant histological subtypes or in more advanced stage of the disease.

CONCLUSIONS

IgG expression in breast cancer cells is correlated with malignancy and AJCC stages of the cancers. This suggests that breast cancer derived IgG may be associated with genesis, development and prognosis of the cancer.

Immunoglobulin G expression and its colocalization with complement proteins in papillary thyroid cancer

Except for the well-known immunoglobulin G (IgG) producing cell types, ie, mature B lymphocytes and plasma cells, various non-lymphoid cell types, including human cancer cells, neurons, and some specified epithelial cells, have been found to express IgG. In this study, we detected the expression of the heavy chain of IgG (IgGγ) and kappa light chain (Igκ) in papillary thyroid cancer cells. Using in situ hybridization, we detected the constant region of human IgG1 (IGHG1) in papillary thyroid cancer cells. With laser capture microdissection followed by RT-PCR, mRNA transcripts of IGHG1, Igκ, recombination activating gene 1 (RAG1), RAG2, and activation-induced cytidine deaminase genes were successfully amplified from isolated papillary thyroid cancer cells. We further confirmed IgG protein expression with immunohistochemistry and found that none of the IgG receptors was expressed in papillary thyroid cancer. Differences in the level of IgGγ expression between tumor size, between papillary thyroid cancer and normal thyroid tissue, as well as between papillary thyroid cancer with and without lymph node metastasis were significant. Taken together, these results indicate that IgG is produced by papillary thyroid cancer cells and that it might be positively related to the growth and metastasis of papillary thyroid cancer cells. Furthermore, it was demonstrated that IgGγ colocalized with complement proteins in the same cancer cells, which could indicate that immune complexes were formed. Such immune complexes might consist of IgG synthesized by the host against tumor surface antigens and locally produced anti-idiotypic IgG with specificity for the variable region of these 'primary' antibodies. The cancer cells might thus escape the host tumor-antigen-specific immune responses, hence promoting tumor progression.

Fibroblasts from Werner syndrome patients: cancer cells derived by experimental introduction of oncogenes maintain malignant properties despite entering crisis

Werner syndrome (WS) results from defects in the gene encoding WRN RecQ helicase. WS fibroblasts undergo premature senescence in culture. Because cellular senescence is a tumor suppressor mechanism, we examined whether WS fibroblasts exhibited reduced tumorigenicity, in comparison to control cells, in a model of experimental conversion of normal human cells to cancer cells. The combination of oncogenic Ras (Ha-Ras(V12G)) and SV40 large T antigen (SV40 LT) causes human cells to acquire neoplastic properties in the absence of telomerase. We found that WS cells could also be converted to a tumorigenic state by these oncogenes, as evidenced by invasion and metastasis of cells implanted in immunodeficient mice. Ras/SV40 LT-expressing cells retained invasiveness and malignant properties even when cells reached crisis in tumors in vivo. High levels of gelatinase were found by an in situ assay in Ras/SV40 LT-expressing cells undergoing crisis. We conclude that, despite evidence of accelerated senescence in WS cells, there is no evidence that the absence of active WRN acts as a barrier to neoplastic transformation. Moreover, we find that tumorigenic human cells retain malignant properties of the cells as they approach and reach crisis.

A case of γ1-heavy chain deposition disease successfully treated with melphalan and prednisolone therapy

Heavy chain deposition disease (HCDD) is characterized by glomerular and tubular deposition of non-amyloidotic monoclonal heavy chains without associated light chains. We describe a case of gamma1-HCDD who presented with nephrotic syndrome, microhematuria, and hypocomplementemia. Renal biopsy showed lobular and nodular glomerulosclerosis along with IgG and C3 deposition. Electron microscopy revealed electron-dense deposits on the glomerular and tubular basement membranes and mesangium. Congo red staining was negative. Staining was positive for IgG1 on glomerular and tubular basement membranes but negative for IgG2-4, kappa and lambda light chains. Staining for the constant heavy chain domains showed the deletion of the first constant heavy chain domain. Thus, we diagnosed gamma1-HCDD. She was considered to be early-stage HCDD because proteinuria and hematuria were not observed before the nephrotic syndrome onset. Melphalan and prednisolone (MP) therapy reduced proteinuria as well as improved renal function and complement levels. Although renal prognosis of HCDD is poor, aggressive chemotherapy with MP may be effective in early-stage HCDD patients.

[Impact of immunoglobulin gene somatic high mutation on prognosis of the chronic lymphocytic leukemia]

There are great differences in the clinical process and prognosis of the chronic lymphocytic leukemia(CLL), the precise diagnosis is of importance to judge prognosis, guide therapy and research pathogenesis mechanism. The variable region mutation of immunoglobulin heavy chain is the most stable molecular index of disease prediction. The patients with sequence of IgHV somatic high mutation usually have a better prognosis and a more longer survival time than those without the mutation. The recent study has found that specific IgHV gene expression also can predict the disease outcome in some cases regardless of mutation. The clinical prognosis of CLL patients can be further stratified by specific IgHV gene expression. In this review, the progress in the research of the clinical significance of specific IgHV gene expression in the chronic lymphocytic leukemia is summarized.

In situ follicular lymphoma associated with progressive transformation of germinal centers

The authors report here a case of in situ follicular lymphoma (FL) associated with progressive transformation of the germinal center (PTGC). A 39-year-old Japanese male developed a mass in the right cervical region. Biopsy of the enlarged lymph node led to a diagnosis of PTGC. Then, 5 years later, the lymphadenopathy recurred. The second biopsy specimens contained numerous germinal centers, including PTGC. Although most follicles were cytologically reactive, a few GCs appeared to be somewhat monotonous, composed predominantly of centrocytes and lacking mitotic figures and tangible body macrophages. Immunohistochemical studies demonstrated that these atypical GCs were CD10+, CD20+, and bcl-2+, with λ-light-chain restriction. A previous report emphasized the differential diagnostic problem between PTGC and the floral variant of FL. However, the present case indicated that in situ FL should be added to the list of differential diagnoses for PTGC.

FoxP3+CD4+ regulatory T cells play an important role in acute HIV-1 infection in humanized Rag2-/-gammaC-/- mice in vivo

The role of FoxP3(+)CD4(+) regulatory T (Treg) cells in HIV-1 disease in vivo is poorly understood due to the lack of a robust model. We report here that CD4(+)FoxP3(+) T cells are developed in all lymphoid organs in humanized Rag2(-/-)gammaC(-/-) (DKO-hu HSC) mice and they display both Treg phenotype and Treg function. These FoxP3(+) Treg cells are preferentially infected and depleted by a pathogenic HIV-1 isolate in HIV-infected DKO-hu HSC mice; and depletion of Treg cells is correlated with induction of their apoptosis in vivo. When CD4(+)CD25(+/hi) Treg cells are depleted with the IL-2-toxin fusion protein (denileukin diftitox), HIV-1 infection is significantly impaired. This is demonstrated by reduced levels of productively infected cells in lymphoid organs and lower plasma viremia. Therefore, FoxP3(+) Treg cells are productively infected and play an important role in acute HIV-1 infection in vivo. The DKO-hu HSC mouse will be a valuable model to study human Treg functions and their role in HIV-1 pathogenesis in vivo.

Assignment of the bovine immunoglobulin gamma heavy chain (IGHG) gene to chromosome 21q24 by in situ hybridization

By the use of in situ hybridization, the bovine immunoglobulin gamma heavy chain (IGHG) gene was assigned to chromosome 21q24. Fifteen percent of the total grains were scored on chromosome 21, with about 65 percent of these grains located on the q24 band. The present results confirm a previous synteny study and provide the precise chromosomal localization of this gene in the cattle genome.

Binding activities and antitumor properties of a new mouse/human chimeric antibody specific for GD2 ganglioside antigen

PURPOSE

We previously generated a mouse monoclonal antibody (mAb) specific for the tumor-associated GD2 ganglioside antigen. Here, we describe the development of a chimeric anti-GD2 mAb for more effective tumor immunotherapy.

EXPERIMENTAL DESIGN

We cloned the cDNA encoding the immunoglobulin light and heavy chains of the 60C3 anti-GD2 mAb, and constructed chimeric genes by linking the cDNA fragments of the variable regions of the murine light and heavy chains to cDNA fragments of the human kappa and gamma1 constant regions, respectively.

RESULTS

The resultant chimeric anti-GD2 mAb, c.60C3, showed identical binding affinity and specificity to that of its murine counterpart. Both c.60C3 and 60C3 were rapidly internalized by tumor cells at 37 degrees C. When human serum and human natural killer cells were used as effectors in complement-mediated cytotoxicity and antibody-dependent cell cytotoxicity, respectively, c.60C3 was more effective in killing GD2-expressing tumor cells. However, c.60C3 was ineffective at inducing cell death by apoptosis, although binding of 60C3 induced apoptotic death in vitro. In an in vivo, GD2-expressing, syngeneic tumor model, i.v. injection of c.60C3, but not of 60C3, significantly suppressed tumor growth in mice (P<0.0005).

CONCLUSION

Immune effector functions mediated by this antibody and its potentially reduced immunogenicity make chimeric c.60C3 a promising therapeutic agent against neuroectodermic tumors.

Identification of ERdj3 and OBF-1/BOB-1/OCA-B as direct targets of XBP-1 during plasma cell differentiation

Plasma cell differentiation is accompanied by a modified unfolded protein response (UPR), which involves activation of the Ire1 and activating transcription factor 6 branches, but not the PKR-like endoplasmic reticulum kinase branch. Ire1-mediated splicing of XBP-1 (XBP-1(S)) is required for terminal differentiation, although the direct targets of XBP-1(S) in this process have not been identified. We demonstrate that XBP-1(S) binds to the promoter of ERdj3 in plasmacytoma cells and in LPS-stimulated primary splenic B cells, which corresponds to increased expression of ERdj3 transcripts in both cases. When small hairpin RNA was used to decrease XBP-1 expression in plasmacytoma lines, ERdj3 transcripts were concomitantly reduced. The accumulation of Ig gamma H chain protein was also diminished, but unexpectedly this occurred at the transcriptional level as opposed to effects on H chain stability. The decrease in H chain transcripts correlated with a reduction in mRNA encoding the H chain transcription factor, OBF-1/BOB-1/OCA-B. Chromatin immunoprecipitation experiments revealed that XBP-1(S) binds to the OBF-1/BOB-1/OCA-B promoter in the plasmacytoma line and in primary B cells not only during plasma cell differentiation, but also in response to classical UPR activation. Gel shift assays suggest that XBP-1(S) binding occurs through a UPR element conserved in both murine and human OBF-1/BOB-1/OCA-B promoters as opposed to endoplasmic reticulum stress response elements. Our studies are the first to identify direct downstream targets of XBP-1(S) during either plasma cell differentiation or the UPR. In addition, our data further define the XBP-1(S)-binding sequence and provide yet another role for this protein as a master regulator of plasma cell differentiation.

Transcriptional silencing of nonsense codon-containing immunoglobulin micro genes requires translation of its mRNA

Eukaryotes have evolved quality control mechanisms that prevent the expression of genes in which the protein coding potential is crippled by the presence of a premature translation-termination codon (PTC). In addition to nonsense-mediated mRNA decay (NMD), a well documented posttranscriptional consequence of the presence of a PTC in an mRNA, we recently reported the transcriptional silencing of PTC-containing immunoglobulin (Ig) mu and gamma minigenes when they are stably integrated into the genome of HeLa cells. Here we demonstrate that this transcriptional silencing of PTC-containing Ig-mu constructs requires active translation of the cognate mRNA, as it is not observed under conditions where translation of the PTC-containing mRNA is inhibited through an iron-responsive element in the 5'-untranslated region. Furthermore, RNA interference-mediated depletion of the essential NMD factor Upf1 not only abolishes NMD but also reduces the extent of nonsense-mediated transcriptional gene silencing (NMTGS). Collectively, our data indicate that NMTGS and NMD are linked, relying on the same mechanism for PTC recognition, and that the NMTGS pathway branches from the NMD pathway at a step after Upf1 function.

Human IgG1 Cgamma1 domain is crucial for the bioactivity of the engineered anti-CD20 antibodies

In this study, we discussed the necessity of human IgG1 Cgamma1 domain for recombinant antibody using computer-aided homology modeling method and experimental studies. The heavy (VH) and light (VL) chain variable regions of 1-28, a murine IgM-type anti-CD20 mAb, were ligated by linker peptide (Gly4Ser)3 to form the single-chain Fv fragment (scFv). Then, the engineered antibody (LH1-3) was generated by fusing scFv with the entire IgG1 heavy constant regions. The 3-D structure of LH1-3 was modeled using computer-aided homology modeling method and the binding activity of LH1-3 was evaluated theoretically. Compared to the 3-D structure of the Fv fragment of the parent antibody, the conformation of the active pocket of LH1-3 was remained because of the rigid support of Cgamma1. Further experimental results of flow cytometry showed that the engineered anti-CD20 antibody possessed specifically binding activity to CD20-expressing target cells. The anti-CD20 antibody fragments could also mediate complement-dependent cytotoxicity (CDC) of human B-lymphoid cell lines. Our study highlights some interests and advantages of a methodology based on the homology modeling and analysis of molecular structural properties.

Reduction of arthritis following intra-articular administration of an adeno-associated virus serotype 5 expressing a disease-inducible TNF-blocking agent

BACKGROUND

In the context of preclinical development, we studied the potential of intra-articular gene delivery using a recombinant adeno-associated virus 5 (rAAV5) encoding a chimeric human tumour necrosis factoralpha (TNFalpha) soluble receptor I linked to a mouse immunoglobulin heavy chain Fc portion (TNF receptor I; TNFRI-Ig).

METHODS

Expression was under control of a nuclear factor kappa B (NFkappaB)-responsive promoter and compared with a cytomegalovirus (CMV) promoter (rAAV5.NFkappaB-TNFRI-Ig and rAAV5.CMV-TNFRI-Ig, respectively).

RESULTS

Fibroblast-like synoviocytes transduced in vitro with rAAV5.NFkappaB-TNFRI-Ig were able to produce TNFRI-Ig protein in response to several stimuli, and this was inhibited upon treatment with a specific NFkappaB blocking agent. A bioassay revealed that the synthesised TNFRI-Ig was bioactive, showing a higher affinity for human than for rat TNFalpha. Transcription of the transgene and protein production were detectable in joints injected with both constructs. No dissemination of the vector was observed outside the joints. A significant reduction in paw swelling was seen in rats treated with rAAV5.NFkappaB-TNFRI-Ig. This clinical effect was accompanied by a decrease in pro-inflammatory cytokine levels and an increase in IL10 expression in the synovium.

CONCLUSION

These results provide evidence that intra-articular gene therapy using rAAV5 encoding TNFRI-Ig may be a safe and feasible approach for the treatment of rheumatoid arthritis. The higher affinity for human TNFalpha suggests that in patients with rheumatoid arthritis the therapeutic effect might be even more pronounced than in rat adjuvant arthritis.

Quantitative assessment of human T lymphocytes in RAG2(-/-)gammac(-/-) mice: the impact of ex vivo manipulation on in vivo functionality

OBJECTIVE

Recent clinical trials of adoptive immunotherapy showed diminished reactivity of human T cells upon ex vivo manipulation. For a safe and effective clinical application of human T cells, it is necessary to improve ex vivo manipulation procedures and evaluate their impact on in vivo functionality. However, there is no preclinical model for quantitative assessment of in vivo functionality of human T cells. In this study, we investigated the feasibility of using the huPBMC- RAG2(-/-)gammac(-/-) xenogeneic mouse model. As a first example, we compared 3 different ex vivo culture conditions for human T cells.

METHODS

RAG2(-/-)gammac(-/-) mice received cultured human T cells that were stimulated via CD3 alone or costimulated via CD28 (CD3/28) and/or human 4-1BB (CD3/28/4-1BB). Engraftment levels and survival of the cells were measured. The dynamics of the human T cell phenotypes were analyzed during culture and in vivo, as well as the mechanism of the xenoresponse.

RESULTS

Engraftment potential was improved twofold for costimulation compared to CD3 alone (p < 0.001). Phenotypic analysis showed a strikingly similar pattern of development towards CD4(+) and CD8(+) effector and effector-memory cells, suggesting antigen-driven survival and expansion. All parameters used to analyze different effects on in vivo T-cell functionality, like culture condition, engraftment levels, survival of the cells over time, or xenogeneic graft-vs-host disease were absolutely independent of the distribution of the T cell population in vivo following contact with xeno-antigen.

CONCLUSION

The huPBMC-RAG2(-/-)gammac(-/-) xenogeneic transplant model is the most sensitive to date for in vivo functional evaluation of human T cells.

NF-kappa B binds to the immunoglobulin S gamma 3 region in vivo during class switch recombination

Ig class switch recombination (CSR) is dependent upon the expression of activation-induced deaminase and targeted to specific isotypes by germ-line transcript expression and isotype-specific factors. NF-kappaB plays critical roles in multiple aspects of B cell biology and has been implicated in the mechanism of CSR by in vitro binding assays and altered S/S junctions derived from NF-kappaB p50-deficient mice. However, the pleiotropic contributions of NF-kappaB to gene expression in B cells has made discerning a direct role for NF-kappaB in CSR difficult. We now observe that binding of NF-kappaB components p50 and p65 is detected on Sgamma3 in vivo following lipopolysaccharide (LPS) activation and repressed by LPS + IL-4, suggesting a direct role for this factor in CSR. In vivo footprinting confirms occupancy of a previously defined NF-kappaB recognition site in Sgamma3 with the same temporal kinetics as found in the chromatin immunoprecipitation analysis. Binding of NF-kappaB components p50 and p65 was also detected on Sgamma1 following B cell activation. H3 histone hyper acetylation at Sgamma1 is strongly correlated with NF-kappaB binding, suggesting that NF-kappaB mediates chromatin remodeling in the Sgamma3 and Sgamma1 region.

Induced Expression of Murine γ2a by CD40 Ligation Independently of IFN-γ

IgG2a, with gamma2a H chains, is important for protection against viruses and other intracellular pathogens. Although a large portion of IgG2a expression is dependent upon IFN-gamma, some germline transcription and switch recombination to the murine gamma2a H chain gene expression are independent of IFN-gamma. We found that agonistic anti-CD40 Abs injected into IFN-gamma-deficient mice induce a > 200-fold increase in the amount of serum Ig2a, while other Ig isotypes are increased by 16-fold or less. In vitro, ligation of CD40 on B cells, without the addition of other B cell activators or cytokines, results in germline transcription and switch recombination that are largely restricted to the gamma2a gene. These results suggest that some immune responses to infectious agents can result in large amounts of IgG2a expression through ligation of CD40, without the expression of IFN-gamma by Th1 or other cells.

Human Regulatory T Cells Control Xenogeneic Graft-versus-Host Disease Induced by Autologous T Cells in RAG2−/−γc−/− Immunodeficient Mice

PURPOSE

Effective prevention of graft-versus-host disease (GvHD) is a major challenge to improve the safety of allogeneic stem cell transplantation for leukemia treatment. In murine transplantation models, administration of naturally occurring CD4+CD25+ regulatory T cells (Treg) can prevent GvHD. Toward understanding the role of human Treg in stem cell transplantation, we studied their capacity to modulate T-cell-dependent xenogeneic (x)-GvHD in a new model where x-GvHD is induced in RAG2-/-gammac-/- mice by i.v. administration of human peripheral blood mononuclear cells (PBMC).

EXPERIMENTAL DESIGN

Human PBMC, depleted of or supplemented with autologous CD25+ Tregs, were administered in mice at different doses. The development of x-GvHD, in vivo expansion of human T cells, and secretion of human cytokines were monitored at weekly intervals.

RESULTS

Depletion of CD25+ cells from human PBMC significantly exacerbated x-GvHD and accelerated its lethality. In contrast, coadministration of Treg-enriched CD25+ cell fractions with autologous PBMC significantly reduced the lethality of x-GvHD. Treg administration significantly inhibited the explosive expansion of effector CD4+ and CD8+ T cells. Interestingly, protection from x-GvHD after Treg administration was associated with a significant increase in plasma levels of interleukin-10 and IFN-gamma, suggesting the de novo development of TR1 cells.

CONCLUSIONS

These results show, for the first time, the potent in vivo capacity of naturally occurring human Tregs to control GvHD-inducing autologous T cells, and indicate that this xenogeneic in vivo model may provide a suitable platform to further explore the in vivo mechanisms of T-cell down-regulation by naturally occurring human Tregs.

De novo human T-cell leukemia virus type 1 infection of human lymphocytes in NOD-SCID, common gamma-chain knockout mice

Human T-cell leukemia virus type 1 (HTLV-1) is the etiologic agent of adult T-cell leukemia, a disease that is triggered after a long latency period. HTLV-1 is known to spread through cell-to-cell contact. In an attempt to study the events in early stages of HTLV-1 infection, we inoculated uninfected human peripheral blood mononuclear cells and the HTLV-1-producing cell line MT-2 into NOD-SCID, common gamma-chain knockout mice (human PBMC-NOG mice). HTLV-1 infection was confirmed with the detection of proviral DNA in recovered samples. Both CD4+ and CD8+ T cells were found to harbor the provirus, although the latter population harbored provirus to a lesser extent. Proviral loads increased with time, and inverse PCR analysis revealed the oligoclonal proliferation of infected cells. Although tax gene transcription was suppressed in human PBMC-NOG mice, it increased after in vitro culture. This is similar to the phenotype of HTLV-1-infected cells isolated from HTLV-1 carriers. Furthermore, the reverse transcriptase inhibitors azidothymidine and tenofovir blocked primary infection in human PBMC-NOG mice. However, when tenofovir was administered 1 week after infection, the proviral loads did not differ from those of untreated mice, indicating that after initial infection, clonal proliferation of infected cells was predominant over de novo infection of previously uninfected cells. In this study, we demonstrated that the human PBMC-NOG mouse model should be a useful tool in studying the early stages of primary HTLV-1 infection.

Genetic diversity at the hinge region of the unique immunoglobulin heavy gamma (IGHG) gene in leporids (Oryctolagus, Sylvilagus and Lepus)

Unlike other species, European rabbit (Oryctolagus cuniculus) possesses only one immunoglobulin gamma class. Allelic diversity at the Ig (immunoglobulin) gamma constant region encoded by the unique IGHG (immunoglobulin heavy gamma) gene is moreover much reduced. In the European rabbit, the genetic variation at IGGH hinge region is limited to a single nucleotide substitution, which causes a Met-Thr interchange at amino acid position 9 (IMGT hinge numbering). We have analysed the diversity at this region more in-depth by, (1) analysing the allelic variation in 11 breeds of domestic European rabbit (Oryctolagus cuniculus cuniculus), and (2) sequencing the gamma hinge exon in wild specimens of six species of rabbit (Oryctolagus and Sylvilagus) and hares (Lepus), including the two Oryctolagus subspecies (O. cuniculus cuniculus and O. cuniculus algirus). It appeared that among leporid species, amino acid changes occur exclusively at positions 8 and 9. However, while position 8 is occupied by either Pro or Ser residues, four different residues can occur at position 9 (Met, Thr, Pro and Leu). This variation concerns sites of potential O-glycosylation and/or proteolytic cleavage, suggesting that the underlying genetic diversity could be the outcome of selection. Preservation of the gamma hinge polymorphism in domestic stocks could therefore be important. We report here a polymerase chain reaction/restriction fragment length polymorphism protocol that has allowed the monitoring of the heterozygosity levels at the gamma hinge in 11 breeds of domestic European rabbit.

Unique risk factors for insertional mutagenesis in a mouse model of XSCID gene therapy

Although gene therapy can cure patients with severe combined immunodeficiency (SCID) syndromes, the clinical occurrence of T cell malignancies due to insertional mutagenesis has raised concerns about the safety of gene therapy. Several key questions have remained unanswered: (i) are there unique risk factors for X-linked SCID (XSCID) gene therapy that increase the risk of insertional mutagenesis; (ii) what other genetic lesions may contribute to transformation; and (iii) what systems can be used to test different vectors for their relative safety? To address these questions, we have developed an XSCID mouse model in which both the Arf tumor-suppressor gene and the gammac gene were ablated. Gene therapy in this animal model recapitulates the high incidence of integration-dependent, T cell tumors that was seen in the clinical trial. Ligation-mediated PCR analysis showed integration sites near or within established protooncogenes (Chd9, Slamf6, Tde1, Camk2b, and Ly6e), demonstrating that T cell transformation was associated with targeting of oncogene loci; however, no integrations within the Lmo2 locus were identified. The X-SCID background in transplanted cells was required for high rate transformation and was associated with expansion of primitive hematopoietic cells that may serve tumor precursors. This model should be useful for testing safety-modified vectors and for further exploring the risk factors leading to insertional mutagenesis in gene therapy trials.

AH Amyloidosis Associated With Lymphoplasmacytic Lymphoma Secreting a Monoclonal γ Heavy Chain Carrying an Unusual Truncated D Segment

To date, the presence of amyloidosis associated with immunoglobulin heavy chain (AH amyloidosis) was reported in only 7 cases. Although AH amyloidosis is caused mainly by plasma cell dyscrasia, as in AL amyloidosis, we report a 61-year-old patient who presented with nephrotic syndrome caused by AH amyloidosis associated with lymphoplasmacytic lymphoma. Biochemical and molecular analyses of the deposited amyloid fibrils and heavy-chain genes of lymphocytes showed that proliferative lymphoma cells produced a gamma heavy chain, not a mu heavy chain, which carried an unusual truncated diversity (D) segment of the variable region. Our results indicate that production of the abnormal heavy chain caused by the partially deleted D segment gene is responsible for gamma heavy-chain-related amyloid fibril formation in this patient.

Tracking germinal center B cells expressing germ-line immunoglobulin gamma1 transcripts by conditional gene targeting

Germinal centers (GCs) represent the main sites for the generation of high-affinity, class-switched antibodies during T cell-dependent antibody responses. To study gene function specifically in GC B cells, we generated Cgamma1-cre mice in which the expression of Cre recombinase is induced by transcription of the Ig gamma1 constant region gene segment (Cgamma1). In these mice, Cre-mediated recombination at the fas, Igbeta, IgH, and Rosa26 loci occurred in GC B cells as early as 4 days after immunization with T cell-dependent antigens and involved >85% of GC B cells at the peak of the GC reaction. Less than 2% of IgM(+) B cells showed Cre-mediated recombination. These cells carried few Ig somatic mutations, expressed germ-line Cgamma1- and activation-induced cytidine deaminase-specific transcripts and likely include GC B cell founders and/or plasma cell precursors. Cre-mediated recombination involved most IgG1, but also a fraction of IgG3-, IgG2a-, IgG2b-, and IgA-expressing GC and post-GC B cells. This result indicates that a GC B cell can transcribe more than one downstream C(H) gene before undergoing class switch recombination. The efficient induction of Cre expression in GC B cells makes the Cgamma1-cre allele a powerful tool for the genetic analysis of these cells, as well as, in combination with a suitable marker for Cre-mediated recombination, the tracking of class-switched memory B and plasma cells in vivo. To expedite the genetic analysis of GC B cells, we have established Cgamma1-cre F(1) embryonic stem cells, allowing further rounds of gene targeting and the cloning of compound mutants by tetraploid embryo complementation.

Biased dA/dT somatic hypermutation as regulated by the heavy chain intronic iEmu enhancer and 3'Ealpha enhancers in human lymphoblastoid B cells

Somatic hypermutation (SHM) in immunoglobulin gene (Ig) variable (V) regions is critical for the maturation of the antibody response. It is dependent on the expression of activation-induced cytidine deaminase (AID) and translesion DNA polymerases in germinal center B cells as well as Ig V transcription, as regulated by the Ig heavy chain (H) intronic enhancer (iEmu) and the 3' enhancer (3'Ealpha) region. We analyzed the role of these cis elements in SHM by stably transfecting Ramos human lymphoblastoid B cells with a rearranged human IgH chain VD (diversity) J (joining) DNA construct containing a V(H) promoter at the 5' end and C(H)1 and C(H)2 exons of Cgamma1 at the 3' end. In this construct, mutations preferentially targeted dA/dT basepairs in the RGYW/WRCY hotspot. Most of the dA/dT mutations and accompanying dC/dG mutations were transitions. Deletion of iEmu resulted in decreased SHM which could be partially restored by insertion of the IgH hs1,2 enhancer. Other two 3'Ealpha enhancers, hs3-hs4, did not significantly increase the mutation frequency, but further strengthened the dA/dT bias. The frequency and spectrum of the mutations were independent of the genomic integration of the transgene or V gene transcription level. Thus, we have established a novel in vitro system to analyze SHM and identify the role of multiple cis-regulatory elements in regulating dA/dT biased SHM. This model system will be useful to further address the role of other cis-regulating elements and recruited trans-acting factors in expressing the modalities of SHM.

Disparate roles of ATR and ATM in immunoglobulin class switch recombination and somatic hypermutation

Class switch recombination (CSR) and somatic hypermutation (SHM) are mechanistically related processes initiated by activation-induced cytidine deaminase. Here, we have studied the role of ataxia telangiectasia and Rad3-related protein (ATR) in CSR by analyzing the recombinational junctions, resulting from in vivo switching, in cells from patients with mutations in the ATR gene. The proportion of cells that have switched to immunoglobulin (Ig)A and IgG in the peripheral blood seems to be normal in ATR-deficient (ATRD) patients and the recombined S regions show a normal “blunt end-joining,” but impaired end joining with partially complementary (1–3 bp) DNA ends. There was also an increased usage of microhomology at the μ-α switch junctions, but only up to 9 bp, suggesting that the end-joining pathway requiring longer microhomologies (≥10 bp) may be ATR dependent. The SHM pattern in the Ig variable heavy chain genes is altered, with fewer mutations occurring at A and more mutations at T residues and thus a loss of strand bias in targeting A/T pairs within certain hotspots. These data suggest that the role of ATR is partially overlapping with that of ataxia telangiectasia–mutated protein, but that the former is also endowed with unique functional properties in the repair processes during CSR and SHM.

Cryopreserved Human B Cells as an Alternative Source for Single Cell mRNA Analysis

Reverse transcription-polymerase chain reaction (RT-PCR) of individual B-lymphocytes has been shown to be a powerful tool for the simultaneous analysis of different mRNA specificities in both malignant and non-malignant B cell subpopulations. However, especially for longitudinal studies, this may also require analyses of cryopreserved cells. Therefore, the current study assessed whether cryopreserved (liquid nitrogen, dimethyl sulfoxide [DMSO]-stored) viable B cells are an alternative source for single cell RT-PCR analysis. Fresh (non-frozen) and post-thawed human peripheral blood B cells were analyzed by fluorescence-activated cell sorting (FACS). As a result, different B cell subpopulations could be reliably stained and separated from both fresh and post-thawed cells by four-color flow cytometry, although slightly diminished fluorescence intensities of some subpopulation markers were observed when analyzing cryopreserved cells. Subsequently, viable individual CD19+CD27+ memory B cells were sorted into single wells and analyzed for the expression of mRNA transcripts of the 'house-keeping gene' glyceraldehyde phosphate dehydrogenase (GAPD), the constitutive B cell homing receptor CXCR4, and immunoglobulin heavy chain variable region (IgVH) genes by nested RT-PCR protocols. Comparing both B cell sources, RT-PCR analysis revealed comparable yields of cells expressing transcripts for the three mRNA specificities tested (GAPD, CXCR4, IgVH) indicating the integrity of the respective mRNAs in cryopreserved B cells. In conclusion, these data indicate that optimally cryopreserved B cells may be an alternative source for single-cell RT-PCR analysis, especially in longitudinal B cell studies. However, the settings for both FACS analysis and RT-PCR should be re-evaluated for each distinct subpopulation and target mRNA of interest when analyzing post-thawed cells.

Gene expression of the constant region of the heavy chain of immunoglobulin G (IgG CRHC) is down-regulated in human decidua in association with preeclampsia

An aberrant interaction at the maternal/fetal interface between the genetically distinct fetal trophoblast cells and cells of the maternal decidua has been proposed as an initiating factor in one of the major complications of human pregnancy, preeclampsia. Biochemical and epidemiological studies suggest that the immune system plays an important role in preeclampsia. Thus, the aim of this study was to determine the decidual gene expression status in preeclampsia of one of the key components of the adaptive immune system. Total RNA was extracted from decidua collected from women with normal pregnancies and those complicated by preeclampsia. Reverse Northern analysis was performed on 72 cDNAs from human decidua and differentially expressed genes identified were analysed further using semi-quantitative RT-PCR and Northern blot analysis. Expression of the gene encoding the constant region of the heavy chain of immunoglobulin G (IgG CRHC) was shown to be down-regulated in association with preeclampsia. These data support the hypothesis that immune maladaptation may play an important role in the pathogenesis of preeclampsia.

Interallelic class switch recombination contributes significantly to class switching in mouse B cells

Except for the expression of IgM and IgD, DNA recombination is constantly needed for the expression of other Ig classes and subclasses. The predominant path of class switch recombination (CSR) is intrachromosomal, and the looping-out and deletion model has been abundantly documented. However, switch regions also occasionally constitute convenient substrates for interchromosomal recombination, since it is noticeably the case in a number of chromosomal translocations causing oncogene deregulation in the course of lymphoma and myeloma. Although asymmetric accessibility of Ig alleles should theoretically limit its occurrence, interallelic CSR was shown to occur at low levels during IgA switching in rabbit, where the definition of allotypes within both V and C regions helped identify interchromosomally derived Ig. Thus, we wished to evaluate precisely interallelic CSR frequency in mouse B cells, by using a system in which only one allele (of b allotype) could express a functional VDJ region, whereas only interallelic CSR could restore expression of an excluded (a allotype) allele. In our study, we show that interchromosomal recombination of V(H) and Cgamma or Calpha occurs in vivo in B cells at a frequency that makes a significant contribution to physiological class switching: trans-association of V(H) and C(H) genes accounted for 7% of all alpha mRNA, and this frequency was about twice higher for the gamma3 transcripts, despite the much shorter distance between the J(H) region and the Cgamma3 gene, thus confirming that this phenomenon corresponded to site-specific switching and not to random recombination between long homologous loci.

The 3' end of the heavy chain constant region locus enhances germline transcription and switch recombination of the four gamma genes

The switch in immunoglobulin (Ig) heavy chain class is preceded by germline transcription and then mediated by a DNA recombination event. To study germline transcription and class switch recombination we used transgenic mice with a 230-kilobase bacterial artificial chromosome that included a rearranged VDJ gene and the entire heavy chain constant region locus. In addition to several lines with intact transgenes, we identified two lines in which the heavy chain locus transgene lacked Cα and everything 3′ of it, including the regulatory elements HS3a, HS1-2, HS3b, and HS4. B cells from both lines with the truncated transgenes make abundant transgenic (Tg) VDJCμ transcripts and IgM protein. Deletion of the 3′ end of the locus results in dramatically reduced expression of both germline transcripts and switched VDJCH transcripts of the γ3, γ2b, γ2a, and ɛ genes. In addition, the transgenes lacking the 3′ end of the locus express reduced amounts of γ1 germline transcripts and 2–3% of the amount of Tg IgG1 in tissue culture compared with intact transgenes. Finally, switch recombination to γ1 is undetectable in the transgenes lacking the 3′ elements, as measured by digestion circularization–polymerase chain reaction or by the expression of VDJCγ1 transcripts.

Immunoglobulin GM and KM genotypes in hepatitis C virus infection

Hepatitis C virus (HCV) is a major health problem, affecting over 170 million people worldwide. HCV causes a wide spectrum of liver disease, varying from persistent to asymptomatic infection. To evaluate the role of immunoglobulin (Ig) GM and KM genes in HCV infection, 191 HCV-infected Thai subjects were studied. These included 43 individuals with transient HCV infection and 148 individuals with persistent chronic HCV infection. The controls consisted of 134 healthy individuals. Several GM and KM alleles were determined by polymerase chain reaction-based methods. The frequency of G1M(f) homozygotes was lower (52.4% vs. 64.2%, P = 0.03) and the frequency of G1M(z) homozygotes was higher (10.5% vs. 3.7%, P = 0.02) in patients than the respective frequencies in controls. These results suggest that GM genotypes make a significant contribution to the risk of acquiring HCV infection.

Germline transcription and switch recombination of a transgene containing the entire H chain constant region locus: effect of a mutation in a STAT6 binding site in the gamma 1 promoter

The switch (S) in H chain class is preceded by germline transcription and then mediated by a DNA recombination event. One of the impediments toward understanding the mechanism is the lack of a system in which a recombinant DNA molecule undergoes cytokine-regulated class S recombination. To study class S recombination, we used transgenic mice with a 230-kb bacterial artificial chromosome that included a rearranged VDJ gene and the entire murine H chain constant region locus. We found that both germline transcription and S recombination to the transgenic gamma1 H chain gene were regulated by IL-4 like that of the endogenous genes. In mice with two or more copies of the H chain locus transgene, both germline transcripts and S recombination took place at levels comparable to those from the endogenous loci. We also prepared a version of the transgene with a 4-bp mutation in a STAT6 binding site in the gamma1 promoter region. On the average, this mutation reduced germline transcription by 80%, but did not change the amount of S recombination in vitro. Among both the wild-type and mutant transgenes, we found no significant correlation between the amount of germline transcripts and the amount of S recombination. We infer that the physiologic level of germline transcription of the gamma1 gene is in excess over the amount required for efficient S recombination.

CpG DNA induces IgG class switch DNA recombination by activating human B cells through an innate pathway that requires TLR9 and cooperates with IL-10

TLRs are pattern recognition receptors that initiate innate immune responses. TLR9 detects microbial DNA with hypomethylated CpG motifs and in humans is preferentially expressed by IFN-alpha-producing plasmacytoid dendritic cells and B cells. In addition to favoring IFN-alpha release, TLR9 signals B cell activation, proliferation, and IgM production. Recent findings suggest that CpG DNA-TLR9 interaction plays a key role in systemic lupus erythematosus and rheumatoid arthritis, two autoimmune disorders characterized by dysregulated production of DNA-reactive IgG. We show that CpG DNA initiates germline C(gamma)1, C(gamma)2, and C(gamma)3 gene transcription by activating B cells through a TLR9-mediated NF-kappaB-Rel-dependent innate pathway that cooperates with IL-10 through STAT proteins and IFN-responsive factors. This pathway is inhibited by chloroquine, a drug that attenuates the clinical manifestations of IgG-mediated autoimmune disorders. Germline C(gamma) gene transcription is associated with up-regulation of activation-induced cytidine deaminase, a key element of the B cell class switch-inducing machinery, and is followed by class switch DNA recombination from C(micro) to C(gamma)1, C(gamma)2, and C(gamma)3. Subsequent IgG production requires additional signals from BCR and a B cell-activating factor of the TNF family (BAFF), produced by dendritic cells upon exposure to IFN-alpha. Our findings suggest that CpG DNA-TLR9 interaction may be important to initiate or amplify early T cell-independent IgG responses against pathogens. This implies that CpG DNA released during infections may exacerbate autoimmunity by stimulating autoreactive B cells to switch from an IgM to a more pathogenic IgG isotype.

Immunoglobulin KM and GM gene polymorphisms modify the clinical presentation of primary Sjögren's syndrome

OBJECTIVE

To investigate whether polymorphism of immunoglobulin (Ig) genes affects susceptibility to or severity of primary Sjogren's syndrome (pSS).

METHODS

Ig gene kappa (KM) and gamma (GM) polymorphisms were analyzed by a polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP) based method in 65 Finnish Caucasian patients with pSS and in 66 healthy controls matched for sex, ethnic origin, and area of residence. Clinical and immunological data on the pSS patients were analyzed in relation to Ig genotypes.

RESULTS

The genotype frequencies of Ig KM and GM genes did not differ between pSS patients and controls. Anti-SSB antibodies were encountered significantly more frequently in pSS patients carrying the KM1 allele than in those without (100% vs 48%, p = 0.016). The pSS patients with the KM1 allele had several signs of immunologically active disease: they had significantly higher erythrocyte sedimentation rate, serum IgA, serum beta2-microglobulin (beta2-m), and plasma IgG1 concentrations than patients without this allele. The pSS patients carrying the GM z allele had a milder form of pSS than those without this determinant. They had less severe labial salivary gland histological findings (grade 3-4 in 60% vs 93%, p = 0.004) and lower plasma IgG3 and serum beta2-m concentrations than those without GM z allele.

CONCLUSIONS

Ig KM and GM genes do not contribute to susceptibility to pSS. The Ig KM1 allele is associated with several markers of immunologically active disease, whereas the Ig GM z allele is associated with milder pSS.

Allogeneic bone marrow transplantation restores IGF-I production and linear growth in a gamma-SCID patient with abnormal growth hormone receptor signaling

Severe combined immunodeficiency (SCID) is a heterogeneous group of disorders characterized by a severe defect of both T- and B-cell immunity, which generally require allogeneic bone marrow transplantation (BMT) within the first years of life. We previously reported a patient affected with an X-linked SCID due to L183S hemizygous missense gamma chain mutation, whose severe short stature was due to a peripheral growth hormone (GH) hyporesponsiveness associated to abnormal GH receptor (GH-R) signal transduction. In this study, we report the effect of BMT on the GH-R/insulin-like growth factor I (IGF-I) axis. After BMT, the patient showed a significant improvement in linear growth and normalization of basal- and GH-stimulated IGF-I values, which paralleled a fully competent immunological reconstitution. This suggests that cells derived from the hematopoietic stem cell may exert an unexpectedly significant role in producing IGF-I. This may also suggest that stem cell-based therapies may be useful for the correction of non-hematopoietic inherited disorders, such as those of GH-R/IGF-I axis.

NF- B elements associated with the Stat6 site in the germline 1 immunoglobulin promoter are not necessary for the transcriptional response to CD40 ligand

Both germline transcription and switch recombination of heavy chain genes are likely to be regulated by cis elements binding transcription factors in the promoter regions of germline immunoglobulin genes. To identify cis-acting elements important in germline transcription of the murine gamma1 heavy chain gene, we have used a transgenic approach. Seventeen kb gamma1 immunoglobulin transgenes with mutations in three NF-kappaB sites in the gamma1 proximal promoter, a putative CD40 response element, are expressed well. Compared to wild-type transgenes, there is no deficiency in the expression of the transgenes with mutations of the three NF-kappaB sites after induction of splenic B cells with IL-4 alone, CD40L, or CD40L + IL-4. There may be a small reduction in the response of these mutant transgenes after induction with LPS + IL-4. We also prepared transgenes that were truncated at -150 (rather than -2100) and therefore included the wild-type Stat6 binding site at -123 and the three wild-type NF-kappaB sites. Nevertheless, gamma1 germline transcripts were not expressed from these transgenes. We conclude that the three proximal NF-kappaB sites are dispensable for expression of gamma1 germline transcripts under most conditions. However, cis-acting elements distal to -150 must be critical to this transcription.

Mapping of a functional recombination motif that defines isotype specificity for mu-->gamma3 switch recombination implicates NF-kappaB p50 as the isotype-specific switching factor

Ig class switch recombination (CSR) requires expression of activation-induced deaminase (AID) and production of germline transcripts to target S regions for recombination. However, the mechanism of CSR remains unclear. Here we show that an extrachromosomal S plasmid assay is AID dependent and that a single consensus repeat is both necessary and sufficient for isotype-specific CSR. Transfected switch substrates specific for mu-->gamma3 and mu-->gamma1 are stimulated to switch with lipopolysaccharide (LPS) alone or LPS and interleukin-4, respectively. An Sgamma3/Sgamma1 substrate containing only three Sgamma3-associated nucleotides reconstituted LPS responsiveness and permitted mapping of a functional recombination motif specific for mu-->gamma3 CSR. This functional recombination motif colocalized with a binding site for NF-kappaB p50, and p50 binding to this site was previously established. We show a p50 requirement for plasmid-based mu-->gamma3 CSR using p50-deficient B cells. Switch junctions from p50-deficient B cells showed decreased lengths of microhomology between Smu and Sgamma3 relative to wild-type cells, indicating a function for p50 in the mechanics of CSR. We note a striking parallel between the affects of p50 and Msh2 deficiency on Smu/Sgamma3 junctions. The data suggest that p50 may be the isotype-specific factor in mu-->gamma3 CSR and epistatic with Msh2.

Use of methotrexate-based peptide substrates to characterize the substrate specificity of prostate-specific membrane antigen (PSMA)

Prostate-Specific Membrane Antigen (PSMA) is a glutamate carboxypeptidase II that is highly expressed by both normal and malignant prostate epithelial cells and by the neovasculature of many tumor types but is not expressed by endothelial cells in normal tissue. PSMA possesses the hydrolytic properties of an N-acetylated alpha-linked acidic dipeptidase (NAALADase) and also functions as a pteroyl poly-gamma-glutamyl carboxypeptidase (i.e., folate hydrolase). Therefore, PSMA can be targeted for activation of peptide-based prodrugs within the extracellular fluid of prostate cancers. In this study, methotrexate-based peptide analogs were evaluated to identify PSMA selective substrates that are also stable to nonspecific hydrolysis in human and mouse plasma. These methotrexate analogs were also characterized for in vitro toxicity against PSMA and nonPSMA producing human cancer cell lines. Analogs containing gamma-linked glutamate residues were most efficiently hydrolyzed by PSMA, but were unstable in plasma. Analogs containing both alpha- and gamma-linked acidic amino acids were less efficiently hydrolyzed by PSMA but were most stable in plasma. Analogs were 5-10 fold more selectively toxic in vitro in the presence of active PSMA. These studies have identified PSMA selective, plasma stable peptide substrates that can be incorporated into prodrugs targeted for activation by PSMA within prostate cancer sites.

Generation and selection of an IgG-driven autoimmune repertoire during B-lymphopoiesis in Ig -deficient/lpr mice

Class switch recombination (CSR) is a well-regulated process that occurs in peripheral lymphoid tissue, and is thought of as an important factor constructing the memory repertoire. We have recently shown that CSR normally occurs during bone marrow (BM) development, and these isotype-switched B cells are negatively selected by Fas signaling. This novel pathway of B cell development may generate a primary repertoire driven by gamma-heavy receptors, the nature of which is yet unknown. To study this gammaH-driven repertoire we used mice lacking IgM-transmembrane tail exon ( micro MT), where B cell development is limited by their ability to undergo CSR. We already showed that lack of Fas signaling rescues development of a significant population of isotype-switched B cells and production of high titers of non-IgM serum antibodies in micro MT mice deficient in Fas ( micro MT/lpr), thereby providing a mouse model allowing the assessment of gammaH-driven repertoire. Using a tissue array and phage display epitope library we report here that IgG repertoire in micro MT/lpr mice is oligo-monoclonal, bearing self-tissue reactivity. This is supported by analysis of the Vkappa utilization in peripheral B cells from micro MT/lpr mice, which revealed a strikingly restricted repertoire. In contrast, micro MT/lpr B cells that are grown in non-selective BM cultures utilize a wide repertoire. These results suggest that the Fas pathway is an important regulator in the generation and selection of an autoimmune gammaH-driven repertoire in vivo.

[Construction of expression vector for human-mouse chimeric antibody and expression of an antibody against human HER2]

AIM

To construct universal eukaryotic expression vector for expressing human-mouse chimeric antibody and have application in expression of PCR-obtained mouse variable region gene fragments in the form of human-mouse chimeric antibody, for the purpose of clinical therapy.

METHODS

By using human Tac antigen signal peptide and kappa chain and gamma 1 heavy chain gene fragments of human Ig, we constructed a versatile expression vector for human-mouse chimeric antibody and used it to transfect cultured 293T cells. The expressed product was detected using RT-PCR, FACS and ELISA.

RESULTS

An expression vector for PCR-derived V genes of mouse Ig as human-mouse chimeric antibody was constructed. The V(L) and V(H) genes encoding mouse anti-human HER2 antibody were amplified with primers designed for this expression system, and an expression vector for chimeric antibody against human HER2 was constructed. By transfection of 293T cells, we demonstrated that a chimeric antibody was produced and secreted to the culture medium.

CONCLUSION

This expression system is useful for antibody engineering for it provides a simple way to express chimeric antibody from V genes of mouse antibody obtained by PCR.

Cutting Edge: IL-21 Is a Switch Factor for the Production of IgG1 and IgG3 by Human B Cells

IL-21 is a cytokine that regulates the activation of T and NK cells and promotes the proliferation of B cells activated via CD40. In this study, we show that rIL-21 strongly induces the production of all IgG isotypes by purified CD19(+) human spleen or peripheral blood B cells stimulated with anti-CD40 mAb. Moreover, it was found to specifically induce the production of IgG(1) and IgG(3) by CD40-activated CD19(+)CD27(-) naive human B cells. Although stimulation of CD19(+) B cells via CD40 alone induced gamma 1 and gamma 3 germline transcripts, as well as the expression of activation-induced cytidine deaminase, only stimulation with both anti-CD40 mAb and rIL-21 resulted in the production of S gamma/S mu switch circular DNA. These results show that IL-21, in addition to promoting growth and differentiation of committed B cells, is a specific switch factor for the production of IgG(1) and IgG(3).

Absence of DNA polymerase eta reveals targeting of C mutations on the nontranscribed strand in immunoglobulin switch regions

Activation-induced cytosine deaminase preferentially deaminates C in DNA on the nontranscribed strand in vitro, which theoretically should produce a large increase in mutations of C during hypermutation of immunoglobulin genes. However, a bias for C mutations has not been observed among the mutations in variable genes. Therefore, we examined mutations in the mu and gamma switch regions, which can form stable secondary structures, to look for C mutations. To further simplify the pattern, mutations were studied in the absence of DNA polymerase (pol) eta, which may produce substitutions of nucleotides downstream of C. DNA from lymphocytes of patients with xeroderma pigmentosum variant (XP-V) disease, whose polymerase eta is defective, had the same frequency of switching to all four gamma isotypes and hypermutation in mu-gamma switch sites (0.5% mutations per basepair) as control subjects. There were fewer mutations of A and T bases in the XP-V clones, similar to variable gene mutations from these patients, which confirms that polymerase eta produces substitutions opposite A and T. Most importantly, the absence of polymerase eta revealed an increase in C mutations on the nontranscribed strand. This data shows for the first time that C is preferentially mutated in vivo and pol eta generates hypermutation in the mu and gamma switch regions.