VH4-21, a human VH gene segment overrepresented in the autoimmune repertoire

The impact of individual clinical features in cold agglutinin disease: hemolytic versus non-hemolytic symptoms

INTRODUCTION

During the last decades, the pathogenesis of cold agglutinin disease (CAD) has been well elucidated and shown to be complex. Several documented or investigational therapies have been made available. This development has resulted in major therapeutic advances, but also in challenges in choice of therapy.

AREAS COVERED

In this review, we address each step in pathogenesis: bone marrow clonal lymphoproliferation, composition and effects of monoclonal cold agglutinin, non-complement mediated erythrocyte agglutination, complement-dependent hemolysis, and other effects of complement activation. We also discuss the heterogeneous clinical features and their relation to specific steps in pathogenesis, in particular with respect to the impact of complement involvement. CAD can be classified into three clinical phenotypes with consequences for established treatments as well as development of new therapies. Some promising future treatment approaches - beyond chemoimmunotherapy and complement inhibition - are reviewed.

EXPERT OPINION

The patient's individual clinical profile regarding complement involvement and hemolytic versus non-hemolytic features is important for the choice of treatment. Further development of treatment approaches is encouraged, and some candidate drugs are promising irrespective of clinical phenotype. Patients with CAD requiring therapy should be considered for inclusion in clinical trials.

B-cell receptor profiling before and after IVIG monotherapy in newly diagnosed idiopathic inflammatory myopathies

OBJECTIVE

To unravel B-cell receptor (BcR) characteristics in muscle tissues and peripheral blood and gain more insight into BcR repertoire changes in peripheral blood in idiopathic inflammatory myopathies (IIMs), and study how this correlates to the clinical response to IVIG.

METHODS

Nineteen treatment-naive patients with newly diagnosed IIM were prospectively treated with IVIG monotherapy. RNA-based BcR repertoire sequencing was performed in muscle biopsies collected before, and in peripheral blood (PB) collected before and nine weeks after IVIG treatment. Results were correlated to patients' clinical improvement based on the total improvement score (TIS).

RESULTS

Prior to IVIG treatment, BcR clones found in muscle tissue could be retrieved in peripheral blood. Nine weeks after IVIG treatment, new patient-specific dominant BcR clones appeared in peripheral blood while pre-treatment dominant BcR clones disappeared. The cumulative frequency of all dominant BcR clones before treatment was significantly higher in individuals who responded to IVIG compared with those who did not respond to IVIG, and correlated with a higher CK. During follow-up, a decrease in the cumulative frequency of all dominant clones correlated with a higher TIS.

CONCLUSION

In treatment-naive patients with newly diagnosed IIM, muscle tissue and peripheral blood share expanded BcR clones. In our study a higher cumulative frequency of dominant BcR clones in blood before treatment was associated with a higher CK and better treatment response, suggesting that response to IVIG may depend on the composition of the pre-treatment BcR repertoire.

Clonal expansion and markers of directed mutation of IGHV4-34 B cells in plasmablasts during Kawasaki disease

Kawasaki disease (KD) is the leading cause of acquired heart disease in children. The cause remains unknown; however, epidemiologic and demographic data support a single preceding infectious agent may lead to KD. A variety of pathophysiologic responses have been proposed, including direct invasion of the coronary arteries, a superantigen response, and a post-infectious autoimmune phenomenon. A role for B cell responses during KD are supported by numerous findings including B cell specific markers identified in genome wide association studies. We have recently published data showing children with KD have similar plasmablast (PB) responses to children with infections. Since during other infections, cells expressing antibodies against the preceding infection are enriched in PBs, we sought to explore the specific antibodies encoded by PBs during KD. In one child we see a massive expansion in IGHV4-34 utilizing antibodies, which has been associated with autoimmunity in the past. We further explored this expansion of IGHV4-34 utilization during the peripheral PB rise with next generation sequencing (NGS) analysis and utilizing newer techniques of chromium chip single cell separation (10x Genomics®). We also utilized peptide array screening to attempt to identify an antigen to the most prolific clones.

Follicular lymphoma subgroups with and without t(14;18) differ in their N-glycosylation pattern and IGHV usage

We previously reported that t(14;18)-negative follicular lymphomas (FL) show a clear reduction of newly acquired N-glycosylation sites (NANGS) in immunoglobulin genes. We therefore aimed to investigate in-depth the occurrence of NANGS in a larger cohort of t(14;18)-positive and t(14;18)-negative FL, including early (I/II) and advanced (III/IV) stage treatment-naive and relapsed tumors. The clonotype was determined by using a next-generation sequencing approach in a series of 68 FL with fresh frozen material [36 t(14;18) positive and 32 t(14;18) negative]. The frequency of NANGS differed considerably between t(14;18)-positive and t(14;18)-negative FL stage III/IV, but no difference was observed among t(14;18)-positive and t(14;18)-negative FL stage I/II. The introduction of NANGS in all t(14;18)-negative clinical subgroups occurred significantly more often in the FR3 region. Moreover, t(14;18)-negative treatment-naive FL, specifically those with NANGS, showed a strong bias for IGHV4-34 usage compared with t(14;18)-positive treatment-naive cases with NANGS; IGHV4-34 usage was never recorded in relapsed FL. In conclusion, subgroups of t(14;18)-negative FL might use different mechanisms of B-cell receptor stimulation compared with the lectin-mediated binding described in t(14;18)-positive FL, including responsiveness to autoantigens as indicated by biased IGHV4-34 usage and strong NANGS enrichment in FR3.

Large-scale analysis of 2,152 Ig-seq datasets reveals key features of B cell biology and the antibody repertoire

Antibody repertoire sequencing enables researchers to acquire millions of B cell receptors and investigate these molecules at the single-nucleotide level. This power and resolution in studying humoral responses have led to its wide applications. However, most of these studies were conducted with a limited number of samples. Given the extraordinary diversity, assessment of these key features with a large sample set is demanded. Thus, we collect and systematically analyze 2,152 high-quality heavy-chain antibody repertoires. Our study reveals that 52 core variable genes universally contribute to more than 99% of each individual's repertoire; a distal interspersed preferences characterize V gene recombination; the number of public clones between two repertoires follows a linear model, and the positive selection dominates at RGYW motif in somatic hypermutations. Thus, this population-level analysis resolves some critical features of the antibody repertoire and may have significant value to the large cadre of scientists.

Light chain skewing in autoantibodies and B-cell receptors of the citrullinated antigen-binding B-cell response in rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic autoimmune disease affecting 1% of the world population. RA is associated with the presence of autoantibodies, of which anti-citrullinated protein antibodies (ACPA) are most prominent. ACPA are produced by citrullinated antigen-binding B cells that have presumably survived tolerance checkpoints. So far, it is unclear how and when such autoreactive B cells emerge. Light chain (LC) rearrangement and mutation rates can be informative with regard to selection steps during B-cell development. Therefore, we studied LC characteristics of ACPA-expressing B cells and secreted ACPA with the aim to better understand the development of this disease-specific, autoreactive B-cell response. Paired ACPA-IgG and ACPA-depleted IgG were isolated from serum (n = 87) and synovial fluid (SF, n = 21) of patients with established RA. We determined the LC composition for each fraction by ELISA using kappa(Igκ)- and lambda(Igλ) LC-specific antibodies. Cellular LC expression was determined using flow cytometry. In addition, we used a B-cell receptor (BCR)-specific PCR to obtain LC variable region sequences of citrullinated antigen- and tetanus toxoid (TT)-binding B cells. In serum, we observed an increased frequency of lambda LC in ACPA-IgG (1.64:1) compared to control IgG (2.03:1) and to the κ/λ ratio reported for healthy individuals (2:1). A similar trend towards higher frequencies of lambda LCs was observed for ACPA-IgG in SF (1.84:1). Additionally, the percentage of Igλ-expressing B cells was higher for citrullinated antigen-binding B cells (51%) compared to TT-specific (43%) and total CD19+CD20+ B cells (36%). Moreover, an increased Igλ percentage was observed in BCR-sequences derived from ACPA-expressing (49%) compared to TT-specific B cells (34%). Taken together, we report an enhanced frequency of lambda LCs in the secreted ACPA-IgG repertoire and, on the cellular level, in BCR sequences of ACPA-expressing B cells compared to control. This skewing in the autoreactive B-cell repertoire could reflect a process of active selection.

Dangerous Liaisons: Gammaherpesvirus Subversion of the Immunoglobulin Repertoire

A common biologic property of the gammaherpesviruses Epstein–Barr Virus and Kaposi sarcoma herpesvirus is their use of B lymphocytes as a reservoir of latency in healthy individuals that can undergo oncogenic transformation later in life. Gammaherpesviruses (GHVs) employ an impressive arsenal of proteins and non-coding RNAs to reprogram lymphocytes for proliferative expansion. Within lymphoid tissues, the germinal center (GC) reaction is a hub of B cell proliferation and death. The goal of a GC is to generate and then select for a pool of immunoglobulin (Ig) genes that will provide a protective humoral adaptive immune response. B cells infected with GHVs are detected in GCs and bear the hallmark signatures of the mutagenic processes of somatic hypermutation and isotype class switching of the Ig genes. However, data also supports extrafollicular B cells as a reservoir engaged by GHVs. Next-generation sequencing technologies provide unprecedented detail of the Ig sequence that informs the natural history of infection at the single cell level. Here, we review recent reports from human and murine GHV systems that identify striking differences in the immunoglobulin repertoire of infected B cells compared to their uninfected counterparts. Implications for virus biology, GHV-associated cancers, and host immune dysfunction will be discussed.

Antibody repertoire analysis in polygenic autoimmune diseases

High-throughput sequencing of the DNA/RNA encoding antibody heavy- and light-chains is rapidly transforming the field of adaptive immunity. It can address key questions, including: (i) how the B-cell repertoire differs in health and disease; and (ii) if it does differ, the point(s) in B-cell development at which this occurs. The advent of technologies, such as whole-genome sequencing, offers the chance to link abnormalities in the B-cell antibody repertoire to specific genomic variants and polymorphisms. Here, we discuss the current research using B-cell antibody repertoire sequencing in three polygenic autoimmune diseases where there is good evidence for a pathological role for B-cells, namely systemic lupus erythematosus, multiple sclerosis and rheumatoid arthritis. These autoimmune diseases exhibit significantly skewed B-cell receptor repertoires compared with healthy controls. Interestingly, some common repertoire defects are shared between diseases, such as elevated IGHV4-34 gene usage. B-cell clones have effectively been characterized and tracked between different tissues and blood in autoimmune disease. It has been hypothesized that these differences may signify differences in B-cell tolerance; however, the mechanisms and implications of these defects are not clear.

Biased immunoglobulin light chain use in the Chlamydophila psittaci negative ocular adnexal marginal zone lymphomas

Ocular adnexal mucosa associated lymphoid tissue lymphomas (OAMALTL) are the most common lymphomas of the eye. The potential roles for specific antigens in these lymphomas are still controversial. Previously we examined IGHV usage and mutations in Chlamydophila (C) psittaci-negative OAMALTL, demonstrating biased use of the IGHV4 family and IGHV4-34 gene and evidence for antigen selection. Herein, we examined the IGKV/IGLV gene usage and mutations in 34 C. psittaci-negative OAMALTL originating from the orbit (15), conjunctivae (14), and lacrimal gland (5). Clonal potentially functional IGKV/IGLV gene sequences were identified in 30 tumors (18 kappa and 12 lambda). An overrepresentation of the IGKV4 family (P < 0.01) was observed. The IGKV3-20*01 allele was used at a greater frequency than in normal peripheral blood B-lymphocytes (P = 0.02) and commonly paired with the IGHV4-34 allele. Twenty-seven of the 30 unique light chain sequences displayed mutations from germline and evidence for antigen selection. Overall our findings demonstrate that in C. psittaci-negative OAMALTL there is a biased usage of IGKV families and genes, which harbor somatic mutations. These findings and the specific paring between the IGKV3-20*01 and IGHV4-34 alleles suggest that specific antigens could play an important role in the pathogenesis of these lymphomas.

Fundamental roles of the innate-like repertoire of natural antibodies in immune homeostasis

The composition of the early immune repertoire is biased with prominent expression of spontaneously arising B cell clones that produce IgM with recurrent and often autoreactive binding specificities. Amongst these naturally arising antibodies (NAbs) are IgM antibodies that specifically recognized amaged and senescent cells, often via oxidation-associated neo-determinants. These NAbs are present from birth and can be further boosted by apoptotic cell challenge. Recent studies have shown that IgM NAb to apoptotic cells can enhance phagocytic clearance, as well as suppress proinflammatory responses induced via Toll-like receptors, and block pathogenic IgG-immune complex (IC)-mediated inflammatory responses. Specific antibody effector functions appear to be involved, as these anti-inflammatory properties are dependent on IgM-mediated recruitment of the early recognition factors of complement. Clinical surveys have suggested that anti-apoptotic cell (AC) IgM NAbs may modulate disease activity in some patients with autoimmune disease. In mechanistic studies, anti-AC NAbs were shown to act in dendritic cells by inhibition of the mitogen-activated protein kinase (MAPK) pathway, a primary signal transduction pathway that controls inflammatory responses. This immunomodulatory pathway has an absolute requirement for the induction of MAPK phosphatase-1. Taken together, recent studies have elucidated the novel properties of a class of protective NAbs, which may directly blunt inflammatory responses through a primitive pathway for regulation of the innate immune system.

Biased use of the IGHV4 family and evidence for antigen selection in Chlamydophila psittaci-negative ocular adnexal extranodal marginal zone lymphomas

Extranodal marginal zone lymphomas (EMZL) are the most common lymphomas in the ocular adnexa. The etiology and potential role for antigenic stimulation in these lymphomas are still controversial. We have examined IGHV gene usage and mutations in 67 Chlamydophila psittaci-negative ocular adnexal EMZL. Clonal IGHV gene sequences were identified in 43 tumors originating from the orbit (19), conjunctivae (18) and lacrimal gland (6). Forty four potentially functional clonal IGHV gene sequences were detected with overrepresentation of the IGHV4 family and IGHV4-34 gene. All but 3 sequences were mutated with the average percent homology to the germ line of 93.5±6.1. Multinomial model and Focused binomial test demonstrated evidence for positive and/or negative antigen selection in 59% of the potentially functional IGHV genes. Intraclonal variation was detected in 8 of 11 tumor specimens. Overall our findings demonstrate that C. psittaci-negative ocular adnexal EMZL exhibit biased usage of IGHV families and genes with evidence for intraclonal heterogeneity and antigen selection in multiple tumors, implicating B-cell receptor-mediated antigen stimulation in the pathogenesis of these lymphomas.

Naive antibody gene-segment frequencies are heritable and unaltered by chronic lymphocyte ablation

A diverse antibody repertoire is essential for an effective adaptive immune response to novel molecular surfaces. Although past studies have observed common patterns of V-segment use, as well as variation in V-segment use between individuals, the relative contributions to variance from genetics, disease, age, and environment have remained unclear. Using high-throughput sequence analysis of monozygotic twins, we show that variation in naive V(H) and D(H) segment use is strongly determined by an individual's germ-line genetic background. The inherited segment-use profiles are resilient to differential environmental exposure, disease processes, and chronic lymphocyte depletion therapy. Signatures of the inherited profiles were observed in class switched germ-line use of each individual. However, despite heritable segment use, the rearranged complementarity-determining region-H3 repertoires remained highly specific to the individual. As it has been previously demonstrated that certain V-segments exhibit biased representation in autoimmunity, lymphoma, and viral infection, we anticipate our findings may provide a unique mechanism for stratifying individual risk profiles in specific diseases.

Chlamydial infection: the link with ocular adnexal lymphomas

Chlamydiae are obligate intracellular bacteria that grow in eukaryotic cells and cause a wide spectrum of diseases. They can establish persistent infections, are mitogenic in vitro, promote polyclonal cell proliferation in vivo and induce resistance to apoptosis in infected cells-properties that might contribute to tumorigenesis. In fact, Chlamydophila psittaci (Cp) has been linked to the development and maintenance of ocular adnexal marginal zone B-cell lymphoma (OAMZL). In this indolent malignancy, Cp is transported by monocytes and macrophages and causes both local and systemic infection. Cp elementary bodies are viable and infectious in the conjunctiva and peripheral blood of patients with OAMZL. Bacterial eradication with antibiotic therapy is often followed by lymphoma regression. Despite recent advances in the understanding of this bacterium-lymphoma association, several questions remain unanswered. For instance, prevalence variations among different geographical areas and related diagnostic and therapeutic implications remain a major investigational issue. We will focus on clinical and therapeutic implications of chlamydial infections in patients with lymphomas and summarize the current knowledge on the association between Cp infection and OAMZL. Available data on the epidemiology, biology and pathogenesis of this association are analyzed and new investigative and clinical approaches are discussed.

[B lymphocyte differentiation in granulomatous tissues of the lung and the nasal mucosa in Wegener's granulomatosis: origin of anti-neutrophil cytoplasmic antibody formation?]

Wegener's granulomatosis (WG) starts with granulomatous inflammation of the respiratory tract before it converts into a potentially organ and life threatening systemic vasculitis associated with anti-neutrophil cytoplasmic antibodies (ANCA). The site of formation of the highly specific ANCA directed against "Wegener's autoantigen" proteinase 3 (PR3) is still unknown. Previously, we have shown that follicle-like B lymphocytic infiltrates in the vicinity to PR3 expressing cells in WG-granulomata. We characterized the immunoglobulin-VH repertoire in lung and nasal granulomata (paraffin embedded) from four WG patients. A total of 115 individual VH genes were characterized and compared to 84 VH genes from the peripheral blood of a healthy donor. We found an increased frequency of mutations with a bias to amino acid exchanges within the antigen binding sites (CDR) 1 and 2 in WG tissue. A large number of mutations led to negatively charged amino acids and may increase affinity to the positively charged PR3. Furthermore, the occurrence of differently mutated members of one B cell clone indicates clonal expansion and intraclonal diversification by an antigen, e.g. PR3. Several WG tissue derived genes displayed similarities to published sequences from peripheral PR3 ANCA producing B cells. Thus, granulomata of the lower and upper respiratory tract contain follicle-like B cell clusters with a selected VH repertoire infiltrate in WG. WG granulomata could be the place of autoantigen presentation and formation of high-affinity ANCA within neoformed ectopic or tertiary lymphoid-like tissue areas.

Ocular adnexal MALT lymphoma: an intriguing model for antigen-driven lymphomagenesis and microbial-targeted therapy

Non-Hodgkin's lymphomas constitute one half of malignancies arising in the orbit and the ocular adnexae. Mucosa-associated lymphoid tissue (MALT)-type lymphoma is the most common histological category in this anatomic region. The incidence of ocular adnexal lymphoma of mucosa-associated lymphoid tissue-type (OAML) is increasing and recent studies offered new relevant insights in molecular, pathogenetic and therapeutic issues on these neoplasms. A pathogenetic model of antigen-driven lymphoproliferation similar to that reported for Helicobacter pylori-related gastric MALT lymphomas has been hypothesized for OAML. This notion is supported by the association between OAML and Chlamydophila psittaci infection, an association that is of likely pathogenetic relevance and may influence both the biological behavior and the therapeutic management of these neoplasms. However, this association displays evident geographical variability indicating that other etiopathogenic agents could be involved. These recent acquisitions coupled with the occurrence of chromosomal translocations and other genetic alterations, as well as additional risk factors like autoimmune disorders have contributed to render OAML an exciting challenge for a broad group of physicians and scientists. OAML is an indolent and rarely lethal malignancy that, in selected patients, can be managed with observation alone. Lymphomatous lesions are frequently responsible for symptoms affecting patient's quality of life, requiring, therefore, immediate treatment. Several therapeutic strategies are available, often associated with relevant side-effects. However, the therapeutic choice in OAML is not supported by consolidated evidence due to the lack of prospective trials. In this review, we analyze the most relevant biological, molecular, pathological and clinical features of OAML and propose some therapeutic guidelines for patients affected by this malignancy.

Epstein-Barr virus and systemic lupus erythematosus

PURPOSE OF REVIEW

Systemic lupus erythematosus is a complex human disease likely influenced by a compilation of necessary, but not individually sufficient, features. Although many genetic and environmental factors are associated, this review will focus on the evolving evidence for key Epstein-Barr virus specific roles.

RECENT FINDINGS

Recent studies have shown additional molecular mimicry mechanisms between early events in lupus autoimmunity and specific Epstein-Barr virus responses. In addition, several recent papers have demonstrated increased Epstein-Barr viral load, increased numbers of latently infected peripheral B cells, impaired functional T cell responses, and association of the presence of Epstein-Barr virus DNA in systemic lupus erythematosus patients compared with controls. Additional work has continued to show association of various aspects of Epstein-Barr virus serology with systemic lupus erythematosus and a recent paper outlines differences in the pediatric systemic lupus erythematosus humoral immune response to Epstein-Barr virus nuclear antigen-1 compared with matched controls.

SUMMARY

This review will briefly outline the recent advances that show serologic, DNA, gene expression, viral load, T cell responses, humoral fine specificity, and molecular mimicry evidence for differences between systemic lupus erythematosus patients and controls and the impact that these findings have on understanding the role of Epstein-Barr virus in systemic lupus.

B lymphocyte maturation in Wegener's granulomatosis: a comparative analysis of VH genes from endonasal lesions

BACKGROUND

Anti-neutrophil cytoplasmic antibodies (ANCA) directed against proteinase 3 (PR3) are highly specific for Wegener's granulomatosis (WG). Evidence for a pivotal role of PR3-ANCA in the induction of vasculitis has been demonstrated. B cell clusters have been observed within endonasal biopsy specimens.

OBJECTIVES

To determine whether B cell selection and maturation take place in granulomatous lesions of WG.

METHODS

Granulomatous lesions and the immunoglobulin (VH) gene repertoire from nasal tissue of six WG patients-two active and two smouldering localised WG (ANCA negative, restricted to respiratory tract), plus one active and one smouldering PR3-ANCA positive generalised WG-were characterised by immunohistochemistry, polymerase chain reaction, cloning, DNA sequencing and database comparison.

RESULTS

B lymphocyte-rich, follicle-like areas were observed proximal to PR3 positive cells and plasma cells in granulomatous lesions; 184 VH genes from these granulomatous lesions were compared with 84 VH genes from peripheral blood of a healthy donor. The mutational pattern of VH genes from active WG resembled memory B cells. Structural homologies of VH genes from granulomatous lesions to PR3-ANCA encoding genes were detected. Significantly more genes (55%, 45%, and 53%, respectively) from active WG compared with the healthy repertoire carried mutations to negatively charged amino acids within the binding site coding regions, favouring affinity to the positively charged PR3.

CONCLUSIONS

Selection and affinity maturation of potentially PR3-ANCA producing autoreactive B cells may start in granulomatous lesions, thereby contributing to disease progression from ANCA negative localised to PR3-ANCA positive generalised WG.

Common patterns of B cell perturbation and expanded V4-34 immunoglobulin gene usage in autoimmunity and infection

Features of the lymphocyte population in systemic lupus erythematosus (SLE) include a disordered B cell profile and production of autoantibodies. An additional distinctive perturbation is the overexpression of V4-34-encoded serum immunoglobulins (Ig). A similar rise in V4-34-encoded Ig occurs in normal subjects following infection with certain herpesviruses, and is found in Epstein-Barr virus (EBV)-associated infectious mononucleosis (IM). To assess common and distinctive features of B cells in patients with SLE and IM, we compared the B cell profile and V4-34 gene involvement in patients with SLE and IM. B cell profiles from patients with IM paralleled those of patients with SLE, showing a differential loss of naïve and memory B cells and the maintenance of plasmablast/early plasma cells. Class-switched V4-34-encoded IgG from plasmablast/early plasma cells was evident both in patients with SLE and IM and revealed common features of oligoclonal expansions with most having undergone somatic hypermutation. It has been proposed that, in healthy individuals, expression of the V4-34 gene is specifically censored prior to isotype switch as a control on autoreactivity. If so, censoring is bypassed following EBV infection, after which equilibrium is restored. Continuing high serum levels in SLE may arise either by disordered regulation, or by subclinical reactivation of endogenous virus.

Update on pediatric systemic lupus erythematosus

PURPOSE OF REVIEW

The purpose of this review is to provide an update on the clinical manifestations of SLE in children. Emerging clues on the pathogenesis of the disease based on recent human studies conducted both in children and adults, will also be summarized.

RECENT FINDINGS

Pediatric Rheumatologists caring for children with SLE face many challenges. As the life expectancy of these patients improves, new recognized complications such as accelerated atherosclerosis and hypertension emerge as major causes of morbidity. However, few longitudinal studies describing the long term outcome of these children, including the impact of disease and treatment on their physical and psychological development are available. Few prospective interventional studies have been carried out to assess the efficacy of established and novel treatments in the pediatric population. Recently, basic studies aimed at understanding the immune alterations underlying this disease have been performed in children. These studies indicate an important role for interferon-alpha (IFN-alpha) in the pathogenesis of this disease and reveal an overall striking homogeneity of leukocyte gene expression profiles in children and adults with SLE. The contribution of novel gene polymorphisms to disease susceptibility and the sequential breakdown of tolerance to nuclear antigens that precedes clinical manifestations in patients with SLE are among the recent studies that are helping us understand the complex SLE puzzle.

SUMMARY

SLE continues to cause significant morbidity in the pediatric age group. A better recognition of the age-specific manifestations and long-term complications of this disease is required to improve its outcome. Understanding its unique pathogenesis will hopefully lead to the development of better, more targeted and less toxic therapies.

Utilization of Ig heavy chain variable, diversity, and joining gene segments in children with B-lineage acute lymphoblastic leukemia: implications for the mechanisms of VDJ recombination and for pathogenesis

Sequence analysis of the immunoglobulin heavy chain genes (IgH) has demonstrated preferential usage of specific variable (V), diversity (D), and joining (J) genes at different stages of B-cell development and in B-cell malignancies, and this has provided insight into B-cell maturation and selection. Knowledge of the association between rearrangement patterns based on updated databases and clinical characteristics of pediatric acute lymphoblastic leukemia (ALL) is limited. We analyzed 381 IgH sequences identified at presentation in 317 children with B-lineage ALL and assessed the V(H)D(H)J(H) gene utilization profiles. The D(H)J(H)-proximal V(H) segments and the D(H)2 gene family were significantly overrepresented. Only 21% of V(H)-J(H) joinings were potentially productive, a finding associated with a trend toward an increased risk of relapse. These results suggest that physical location at the V(H) locus is involved in preferential usage of D(H)J(H)-proximal V(H) segments whereas D(H) and J(H) segment usage is governed by position-independent molecular mechanisms. Molecular pathophysiology appears relevant to clinical outcome in patients who have only productive rearrangements, and specific rearrangement patterns are associated with differences in the tumor biology of childhood ALL.

Semiquantitative and qualitative assessment of B-lymphocyte V H repertoire by a fluorescent multiplex PCR

We established a new tool to perform semiquantitative and qualitative screening for V(H) gene usage frequency during IgH rearrangements in human B-lymphocytes. In two separate multiplex PCRs, the rearranged VDJ regions were amplified with V(H) family-specific primers labeled with different fluorescent dyes (FAM, HEX, NED, or ROX). The relative amount of each of the particular V(H) family products and their ratios were determined by fragment analysis on a ABI PRISM 377 sequencer. We verified that the fluorescent multiplex PCR (FMPCR) shows high specificity and sensitivity, acceptable reproducibility and reliability. Data obtained were well in agreement with results revealed by sequencing following single-cell PCR. Ten healthy volunteers showed a comparable semiquantitative V(H) family distribution. The FMPCR also correctly detected a monoclonal peak in a CLL patient. Thus, labeling primers with various fluorescent dyes allows for an assessment of V(H) family usage and an immediate determination of the involved V(H) gene family if any clonal peaks are present. This method provides a quick, easy, and reliable tool for V(H) repertoire screening of larger populations of patients suffering from diseases with changes in the V(H) repertoire allowing for selection of cases worth a more detailed and cumbersome sequence analysis later on.

Diversity and somatic hypermutation of the Ig VHDJH, V kappa J kappa, and V lambda J lambda gene segments in lymphoma B cells: relevance to the origin of the neoplastic B cell clone

Burkitt's lymphoma (BL) is a malignancy of B cells characterized by chromosomal translocations involving the immunoglobulin (Ig) and c-MYC gene loci. To address the putative role of antigen in the clonal expansion of these neoplastic B cells, we analyzed the VHDJH and VLJL gene segments expressed by the established cell lines derived from six endemic BL and six sporadic BL. Eight BL cell lines used genes of the VH3 family, two of the VH4, and two of the VH1. Eight VL chains were kappa (four members of the V kappa3, two of the V kappa1, and two of the V kappa2 subgroups) and four lambda (three members of the V lambda1 and one of the Vl ambda3 subgroup). The VH gene utilization was stochastic (i.e., it reflected the relative representation of the different VH gene family members in the human haploid genome). In contrast, the VL gene utilization was skewed toward the overutilization of the V kappa3 and V lambda1 gene subgroups. When compared with those of the respective germline genes, the sequences of the expressed Ig VDJ genes displayed nucleotide differences that resulted from somatic hypermutation. In three endemic and three sporadic BL cells, nucleotide changes yielding amino acid substitutions segregated within the complementarity determining region, indicating the application of a positive pressure for replacement mutations and suggesting that these neoplastic lymphocytes underwent a process of clonal selection driven by antigen, perhaps emerging from or transitioning through germinal centers.

Vulnerability to stress among women in chronic pain from fibromyalgia and osteoarthritis

In two investigations, we studied vulnerability to the negative effects of stress among women in chronic pain from 2 types of musculoskeletal illnesses, fibromyalgia syndrome (FMS) and osteoarthritis (OA). In Study 1, there were 101 female participants 50 to 78 years old: 50 had FMS, 29 had OA knee pain and were scheduled for knee surgery, and 22 had OA but were not planning surgery. Cross-sectional analyses showed that the three groups were comparable on demographic variables, personality attributes, negative affect, active coping, and perceived social support. As expected, FMS and OA surgery women reported similar levels of bodily pain, and both groups scored higher than OA nonsurgery women. However, women with FMS reported poorer emotional and physical health, lower positive affect, a poorer quality social milieu, and more frequent use of avoidant coping with pain than did both groups of women with OA. Moreover, the perception and use of social support were closely tied to perceived social stress only among the FMS group. In Study 2, we experimentally manipulated negative mood and stress in 41 women 37 to 74 years old: 20 women had FMS, and 21 women had OA. Participantsfrom each group were randomly assigned to either a negative mood induction or a neutral mood (control) condition, and then all participants discussed a stressful interpersonal eventfor 30 min. Stress-related increases in pain were exacerbated by negative mood induction among women with FMS but not women with OA, and pain during stress was associated with decreases in positive affect in women with FMS but not women with OA. These findings suggest that among women with chronic pain, those with FMS may be particularly vulnerable to the negative effects of social stress. They have fewer positive affective resources, use less effective pain-coping strategies, and have more constrained social networks than their counterparts with OA, particularly those who experience similar levels ofpain. They also seem to experience more prolonged stress-related increases in pain under certain circumstances, all of which may contribute to a lowering of positive affect and increased stress reactivity over time.

Regulation of inherently autoreactive VH4-34 B cells in the maintenance of human B cell tolerance

The study of human B cell tolerance has been hampered by difficulties in identifying a sizable population of autoreactive B lymphocytes whose fate could be readily determined. Hypothesizing that B cells expressing intrinsically autoreactive antibodies encoded by the VH4-34 heavy chain gene (VH4-34 cells) represent such a population, we tracked VH4-34 cells in healthy individuals. Here, we show that naive VH4-34 cells are positively selected and mostly restricted to the follicular mantle zone. Subsequently, these cells are largely excluded from the germinal centers and underrepresented in the memory compartment. In healthy donors but not in patients with systemic lupus erythematosus (SLE), these cells are prevented from differentiating into antibody-producing plasma cells. This blockade can be overcome ex vivo using cultures of naive and memory VH4-34 cells in the presence of CD70, IL-2, and IL-10. VH4-34 cells may therefore represent an experimentally useful surrogate for autoantibody transgenes and should prove valuable in studying human B cell tolerance in a physiological, polyclonal environment. Our initial results suggest that both positive and negative selection processes participate in the maintenance of tolerance in autoreactive human B cells at multiple checkpoints throughout B cell differentiation and that at least some censoring mechanisms are faulty in SLE.

Circulating human B cells that express surrogate light chains display a unique antibody repertoire

Circulating human B cells that coexpress V-preB and conventional L chains (V-preB+L+ B cells) are a recently described subset of B cells that express Abs with features of self-reactivity. Initial analysis of V-preB+L+ B cells was limited to Ig-kappa and to the small, underused VH5 family. To determine whether Abs commonly expressed by V-preB+L+ B cells show similar features, we analyzed Ig H chains from three highly expressed VH families, VH1, VH3, and VH4, and Ig-lambda. We find that VH1 and VH3 Abs expressed by V-preB+L+ B cells resemble VH5 in that they display increased JH6 use, long CDR3s, and an increased frequency of D-D fusions. Abs in all three of these VH families also show skewed D reading frame use resulting in predominance of hydrophobic amino acids, which are counterselected in conventional B cells. Like Ig-kappa genes, the Ig-lambda genes in V-preB+L+ B cells show long CDR3s, but they differ from Ig-kappa genes in that they display no evidence of receptor editing. We conclude that a large number of H and L chain Abs expressed by V-preB+L+ B cells display features associated with self-reactive Abs.

Immunoglobulin gene mutations and frequent use of VH1-69 and VH4-34 segments in hepatitis C virus-positive and hepatitis C virus-negative nodal marginal zone B-cell lymphoma

Nodal marginal zone B-cell lymphoma (NMZL) is actually considered as a distinct entity that must be distinguished from extra-nodal and splenic marginal zone lymphomas. To define the cell origin and the role of antigen stimulation we determined the nucleotide sequence of the tumor-related immunoglobulin heavy chain variable genes in 10 cases of NMZL. The results were also evaluated on the basis of the presence of chronic hepatitis C virus (HCV) infection. All 10 cases harbored VH somatic mutations with a sequence homology compared to the closest germline gene, ranging from 83.33 to 98.28%. Interestingly, different VH segments were preferentially used in HCV-positive and HCV-negative patients: three of five HCV-negative NMZLs used a VH4-34 segment joined with different D and JH segments whereas three of five HCV-positive NMZLs used a VH1-69 gene joined with a D3-22 and a JH4 segment, with very strong similarities in the CDR3s among the three different cases. These data indicate: 1) NMZL is derived from B cells that have experienced the germinal center reaction; 2) the preferential usage of a VH1-69 segment in the majority of the HCV-positive NMZL cases with similar CDR3s suggests the presence of a common antigen, probably a HCV antigen epitope, involved in the B-cell selection; and 3) the use of a VH4-34 segment suggests a role of yet unknown B-cell superantigen(s) in the selection of tumor B-cell precursors in HCV-negative NMZL.

Susceptibility of B-cell lymphoma to human antibodies encoded by the V4-34 gene

Our previous studies have shown that mAbs derived from the human V4-34 gene bind and kill human B-lymphocytes via membrane disruption. This study demonstrates the cytotoxicity of two V4-34 encoded mAbs, 216 and Z2D2, towards human B-cell lymphoma. In vitro, 216 and Z2D2 are cytotoxic to a variety of B-cell lymphomas obtained from patient biopsies. In vivo, increased survival was observed with both mAbs in a lymphoma model developed in scid mice with human B-cell line Nalm-6. Studies in mice show that these mAbs are well tolerated with minimum side effects. Since 216 and Z2D2 show increased toxicity towards cycling cells, V4-34 mAb-based therapy can be additive with drugs that block cell-cycle progression. Stem cells that are V4-34 mAb ligand negative would not be depleted. Together, these studies recommend an evaluation of the two completely human mAbs in a phase I trial for B-cell lymphoma.

Nucleotide sequence analysis of a human monoclonal antibody TONO-1 with cytotoxic potential for T-leukemia/lymphoma cells

A human monoclonal antibody (HuMab) TONO-1 (IgM, lambda) recognizes cell surface antigens associated primarily with human T-leukemia/lymphoma cells. In this study, we investigated the reactivity against T-leukemia/lymphoma cells in detail, cytotoxic potential and primary nucleotide and deduced amino acid sequences of the rearranged heavy and light chains of the HuMab TONO-1. Expression of the molecules (TONO-1 Ags) detected by a HuMab TONO-1 was significantly heterogeneous even in the same T-leukemia/lymphoma cell lines HPB-MLT and MOLT-4F. The flow cytometric curves showed an unusual broad-based spread of fluorescence intensity. HuMab TONO-1 was shown to have the ability to kill the T-leukernia/lymphoma cells efficiently in the presence of rabbit complements. However, HuMab TONO-1 did not demonstrate significant antibody-dependent cellular cytotoxic activity. Furthermore, HuMab TONO-1 heavy and light chain variable regions were cloned, sequenced and analyzed. HuMab TONO-1 uses a V(H) gene member of the V(H)IV gene family V(H)71-4, and is productively rearranged with the germ line D(H) gene D(XP')1, and the germ line J(H)5 gene with multiple somatic mutations. HuMab TONO-1 Vlambda belongs to the lambda light chain variable subgroup I family and is derived from the Vlambdalc germ line gene Humlv1042, and germ line gene Jlambda1 without somatic mutations. The results reveal that the production of HuMab TONO-1, with cytotoxic potential for human T-leukemia/lymphoma cells, is achieved by rearrangement of the V(H)71-4/Humlv1042 germ line variable region gene combination, that is associated with the autoimmune repertoire.

B lymphocyte involvement in ankylosing spondylitis: the heavy chain variable segment gene repertoire of B lymphocytes from germinal center-like foci in the synovial membrane indicates antigen selection

The synovial membrane (SM) of affected joints in ankylosing spondylitis (AS) is infiltrated by germinal center-like aggregates (foci) of lymphocytes similar to rheumatoid arthritis (RA). We characterized the rearranged heavy chain variable segment (VH) genes in the SM for gene usage and the mutational pattern to elucidate the B lymphocyte involvement in AS. Cryosections from an AS-derived SM were stained for B and T lymphocytes. B cells were isolated from different areas of a focus. The rearranged VH genes were amplified by semi-nested polymerase chain reaction (PCR) using oligonucleotides specific for the six different VH families and heavy chain joining segments (JHs). PCR products were cloned and sequenced.Fifty-nine of 70 different heavy chain gene rearrangements were potentially functional. Most of the rearranged genes were mutated (range, 1-15%). Thirty of 70 products had a mutational pattern typical for antigen selection. Most of the rearranged VH genes belonged to the VH3 family (54%), consistent with data from healthy donors and patients with RA, while VH4 genes, in contrast to RA, were identified less frequently (10%) and VH5 genes were over-represented (11%). In contrast to RA, neither VH6 genes nor the autoimmunity-prone VH4-34 were seen, whereas another autoimmunity-prone gene, V3-23, was predominantly used (11%). One VH1-derived and one VH3-derived B cell clone were expanded. CDR3 were shorter and more variable in length than in RA. Comparable with RA and reactive arthritis, there is a biased repertoire of selected VH genes, whereas the panel of represented genes is different and less clonal expansion was observed.

Delineation of the human systemic lupus erythematosus anti-Smith antibody response using phage-display combinatorial libraries

The anti-Smith (Sm) autoantibody response is highly specific for systemic lupus erythematosus and is predominantly targeted to the Sm-B/B' and -D1 polypeptides. In all animal species thus far studied, anti-Sm Abs initially recognize proline-rich epitopes in the carboxyl terminus of the Sm-B/B' protein and subsequently to multiple other epitopes in B/B' and D. The absence of appropriate mAbs has limited our understanding of the genetic and structural basis of this autoimmune response. Using phage-display technology and lymphocytes from a systemic lupus erythematosus patient we have generated the first and only panel of human IgG anti-Sm mAbs thus far available. These Abs reproduced to a remarkable extent the serological reactivity of the patient. Epitope mapping and genetic studies revealed that the anti-Sm response is produced by distinct B cell clones with restricted epitope reactivity. All of the Abs in our study were exclusively encoded by different members of the V(H)4 gene family. On the aggregate, our results demonstrate that combinatorial libraries can recapitulate the immune repertoire of peripheral blood B memory cells and that epitope spreading appears to occur through the sequential recruitment of nonclonally related autoreactive B cell clones.

Primary CNS lymphoma: clinical presentation, pathological classification, molecular pathogenesis and treatment

Primary CNS lymphomas (PCNSL) represent malignant non-Hodgkin's B cell lymphomas, which are confined to the central nervous system. They show a dramatic increase in frequency in the immunocompromised as well as in the immunocompetent population. Recent studies have identified germinal center B cells as the cellular origin of PCNSL; however, the details of their molecular pathogenesis still remain to be elucidated. Treatment recommendations are not clearly established. Radiotherapy (RT) is efficient in terms of tumor response, but not curative. Median survival after RT alone is about 1 year. According to the results of uncontrolled studies the combination of RT and chemotherapy based on high-dose methotrexate (HD-MTX) is most efficient in terms of survival rates. However, long-term neurotoxicity overshadows treatment efficacy, especially in patients over 60 years of age. The authors favor the systematic evaluation of chemotherapy alone with protocols including HD MTX, because unicenter results are promising in terms of both survival as well as quality of life in long term survivors.

Immunoglobulin E antibodies of atopic individuals exhibit a broad usage of VH-gene families

The term 'atopy' describes the genetically determined tendency to mount immunoglobulin E (IgE) antibody responses against per se harmless antigens (allergens). In this study we investigated the usage of VH families in the formation of IgE antibodies in 10 patients suffering from mucosal and/or skin manifestations of atopy. IgE antibody reactivities to exogenous allergen sources as well as to autoallergens were determined and, by immunoabsorption, it was demonstrated that allergen-specific IgE accounted for most of the total serum IgE levels in these patients. Using primers with specificity for the VH1-6 gene families and a primer specific for the first constant region of human IgE, cDNAs coding for IgE heavy chain fragments were amplified using the reverse transcription-polymerase chain reaction (RT-PCR) from peripheral blood lymphocytes of the 10 atopic individuals. Hybridization of the heavy chain-encoding cDNAs with an IgE-specific internal oligonucleotide probe revealed a broad usage of all VH-gene families in the atopic individuals. The spectrum of VH families used in a given atopic individual was neither associated with the type or severity of clinical symptoms nor with the number of allergens recognized. The fact that allergen-specific IgE antibodies in atopic individuals originate from a broad variety of B cells thus reflects the activation of multiple B-cell clones during allergen sensitization. This finding should be borne in mind if therapeutic strategies for Type I allergy are considered that aim at a clonal elimination of allergen-specific B cells.

Recognition of auto- and exoantigens by V4-34 gene encoded antibodies

The antigenic specificities of 24 V4-34-encoded monoclonal antibodies were compared with the amino acid sequence. The specificities were divided into three categories, red blood cells, B lymphocytes and auto/exoantigens. Six anti-I monoclonal antibodies, with multiple substitutions in their VH region, did not bind B lymphocytes or auto/exoantigens. Reactivity to these two antigens segregated with the 16 anti-i monoclonal antibodies, which were derived from the near germline V4-34 gene. All anti-i monoclonal antibodies bound B lymphocytes, albeit with varying intensities. B-cell binding correlated with basic amino acids in the VH-CDR3. Reactivity to auto/exoantigens was demonstrated only by a subset anti-i monoclonal antibodies and did not correlate with B-lymphocyte or i-antigen binding. These anti-ssDNA reactive monoclonal antibodies had basic amino acids in the VH-CDR3, strongly supporting the suggested role of arginine in DNA binding. However, an arginine-rich CDR3 was not enough to ensure DNA reactivity, since six other anti-i monoclonal antibodies that fulfilled this criteria did not bind ssDNA. Thus it is possible that the anti-DNA reactivity of V4-34-encoded monoclonal antibodies is mediated by the classic antigen-binding groove generated by the CDRs of the heavy/light chains. In contrast, anti-B-cell/i-antigen reactivity is mediated, unconventionally, by the V4-34 protein with a dominant influence of the VH-CDR3.

Primary central nervous system lymphomas are derived from germinal-center B cells and show a preferential usage of the V4-34 gene segment

Primary central nervous system lymphomas (PCNSLs) have recently received considerable clinical attention due to their increasing incidence. To clarify the histogenetic origin of these intriguing neoplasms, PCNSLs from 10 HIV-negative patients were analyzed for immunoglobulin (Ig) gene rearrangements. All tumors exhibited clonal IgH gene rearrangements. Of the 10 cases, 5 used the V4-34 gene segment, and all of these lymphomas shared an amino acid exchange from glycine to aspartate due to a mutation in the first codon of the complementarity-determining region 1. No preferential usage of D(H), J(H), V(kappa), J(kappa), V(lambda), or J(lambda) gene segments was observed. All potentially functional rearrangements exhibited somatic mutations. The pattern of somatic mutations indicated selection of the tumor cells (or their precursors) for expression of a functional antibody. Mean mutation frequencies of 13. 2% and 8.3% were detected for the heavy and light chains, respectively, thereby exceeding other lymphoma entities. Cloning experiments of three tumors showed ongoing mutation in at least one case. These data suggest that PCNSLs are derived from highly mutated germinal-center B cells. The frequent usage of the V4-34 gene and the presence of a shared replacement mutation may indicate that the tumor precursors recognized a shared (super) antigen.

Rheumatoid factor isotype switch and somatic mutation variants within rheumatoid arthritis synovium

The presence of clonally-related B-lymphocyte aggregates within synovial lining tisue of rheumatoid arthritis (RA) patients suggests a germinal centre-like reaction, which may hold implications for disease pathogenesis and the causes of chronic inflammation. We studied 250 rheumatoid factor (RF) heavy-chain sequences cloned from the synovium of three patients with RA, to determine whether they undergo both somatic mutation and isotype switching consistent with this hypothesis. Size analysis of immunoglobulin heavy-chain cDNAs from synovial RF+ B cells revealed oligoclonal RF+ populations and identically-sized VH-D-JH transcripts of different immunoglobulin isotypes. Sequencing of individual inserts selected from cloned immunoglobulin heavy-chain cDNAs demonstrated a clonal relationship between immunoglobulin M (IgM) RF and IgA RF, suggesting that this isotype switch occurred in synovium. Furthermore, most somatic mutations were found to have occurred after this isotype switch. This finding suggests that the RA synovial microenvironment sustains somatic mutation and isotype switching in RF-specific B lymphocytes akin to secondary lymphoid organs.

CDR3 sequences of MALT lymphoma show homology with those of autoreactive B-cell lines

We have examined the CDR3 sequence and adjacent regions of immunoglobulin genes from B-cell lymphoma of mucosa-associated lymphoid tissue (MALT). Twenty-nine sequences (15 sequences from 13 low-grade MALT lymphomas, marginal zone B-cell lymphomas; 7 sequences from 6 high-grade MALT lymphomas; 7 sequences from 7 diffuse large cell lymphomas) were obtained after cloning of the polymerase chain reaction-amplified segments. In the low-grade MALT, high-grade MALT and diffuse large cell lymphomas, the mean length of the CDR3 region was 47.6+/-10.31 (range 21 to 60), 38.71+/-10.37 (range 27 to 57) and 40.86+/-3.34 (range 39 to 48) nucleotides, respectively. The length of the CDR3 region was significantly greater in the low-grade MALT lymphoma group than in the other two groups. CDR3 sequences in lymphoma cell clones of 14 cases showed 60 to 81% homology with autoantibody-associated lymphocyte clones including rheumatoid factor. The incidences of these autoantibody-associated lymphocyte clones were higher in the high-grade MALT (4/6) and diffuse large lymphomas (5/7) than in the low-grade MALT lymphoma (5/13). Cases with more than 70% homology at the nucleotide level were found to have 71 to 82% homology with autoantibodies at the protein level in the low-grade MALT lymphomas (2/13), and 67% homology in the high-grade MALT lymphomas (2/7). These results indicate that MALT lymphomas may be derived from the malignant transformation of autoreactive B-cells.

A comparison of the characteristics of circulating anti-myeloperoxidase autoantibodies in vasculitis with those in non-vasculitic conditions

Although circulating anti-neutrophil cytoplasmic antibodies (ANCA) specific for myeloperoxidase (MPO) are strongly associated with the presence of vasculitis, they have been described in sera from patients with other conditions. High levels of anti-MPO antibodies can also persist in sera from patients with vasculitis despite the achievement of clinical remission. One possible interpretation is that a potentially pathogenic subset of anti-MPO antibodies exists, which is only present in patients with active vasculitis. We therefore compared the characteristics of anti-MPO antibodies in sera from patients with active vasculitis (n = 18) with those present in remission (n = 9) and in a disease control group (n = 10) without clinical evidence of vasculitis. The class, subclass and ability of anti-MPO antibodies from the three groups of patients to recognize three different conformational epitopes were analysed using ELISA-based techniques. The expression of an idiotope, designated 9G4, was also examined. Epitope recognition by anti-MPO antibodies from all patients tested was found to be similar. Sera from patients with active vasculitis showed an over-representation of IgG4 subclass anti-MPO antibodies and a more frequent presence of IgM class anti-MPO antibodies. In disease controls, IgG1 anti-MPO antibodies were predominant. In vitro, neutrophil activation by ANCA has been shown to be dependent on engagement of neutrophil FcgammaRIIa receptors following binding of these autoantibodies to surface-expressed ANCA antigens. We found that active vasculitis may be associated with the presence of circulating anti-MPO antibodies which do not significantly bind this receptor, suggesting that mechanisms other than those dependent on FcgammaRIIa binding should be explored. In addition, the expression of the 9G4 idiotope on anti-MPO antibodies in 60% (12/18) of patients with active vasculitis and 20% (2/10) of disease control patients may indicate a common origin for anti-MPO antibodies in different individuals.

Chronic lymphocytic leukemia B cells express restricted sets of mutated and unmutated antigen receptors

To better understand the stage(s) of differentiation reached by B-type chronic lymphocytic leukemia (B-CLL) cells and to gain insight into the potential role of antigenic stimulation in the development and diversification of these cells, we analyzed the rearranged VH genes expressed by 83 B-CLL cells (64 IgM+ and 19 non-IgM+). Our results confirm and extend the observations of a bias in the use of certain VH, D, and JH genes among B-CLL cells. In addition, they indicate that the VH genes of approximately 50% of the IgM+ B-CLL cells and approximately 75% of the non-IgM+ B-CLL cells can exhibit somatic mutations. The presence of mutation varies according to the VH family expressed by the B-CLL cell (VH3 expressers displaying more mutation than VH1 and VH4 expressers). In addition, the extent of mutation can be sizeable with approximately 32% of the IgM+ cases and approximately 68% of the non-IgM+ cases differing by > 5% from the most similar germline gene. Approximately 20% of the mutated VH genes display replacement mutations in a pattern consistent with antigen selection. However, CDR3 characteristics (D and JH gene use and association and HCDR3 length, composition, and charge) suggest that selection for distinct B cell receptors (BCR) occurs in many more B-CLL cells. Based on these data, we suggest three prototypic BCR, representing the VH genes most frequently encountered in our study. These data suggest that many B-CLL cells have been previously stimulated, placing them in the "experienced" or "memory" CD5(+) B cell subset.

Somatic mutation in autoantibody-associated VH genes of circulating IgM+IgD+ B cells

Naive B cells expressing IgM and IgD on their surface have no or little somatic mutations in V genes. We have demonstrated that the human IgM+IgD+B cell clone (0-81), which expresses nephritogenic idiotypes, produces IgM anti-DNA antibodies which show monospecificity to DNA. Using a DNA probe which specifically links to the VH gene of antibody 0-81, we identified the counterpart germ-line V gene of 0-81, V3-7, which appears to be used by pathogenic autoantibodies in humans. Clone 0-81, which may belong to naive B cells in terms of cell phenotype, uses a somatically mutated V3-7 gene. We further studied DNA sequences of V3-7 genes in circulating IgM+IgD+B cells from normal subjects and patients with systemic lupus erythematosus (SLE). The results revealed that rearranged V3-7 genes in IgM+IgD+B cells from patients with SLE contained somatically mutated sequences at significantly increased frequencies. These data indicate an abnormal maturation of B cells in autoimmune states that may be associated with an escape of self-reactive B cells from the elimination process in the germinal center.

The immunology of AIDS-associated lymphomas

Lymphomas that occur in patients with human immunodeficiency virus (HIV) infection are predominantly of B-cell origin and subsets show evidence for Epstein-Barr virus (EBV) infection or chromosomal translocations in the c-myc locus. The only subset of lymphoma clearly related to the immunodeficiency caused by HIV infection (similar to transplantation-associated lymphomas) is the EBV+ primary central nervous system lymphoma. The systemic AIDS-related lymphomas (ARLs) represent a complex set of disease processes histologically categorized as large cell or small non-cleaved (Burkitt's-like) lymphomas. Molecular analyses of the ARLs have demonstrated polyclonal lymphomas as likely early representatives of monoclonal immunoglobulin (Ig)-expressing B-cell lymphomas. Variable region analysis of lymphoma-associated Ig has shown evidence for extensive somatic mutation with little evidence for appropriate affinity maturation. These observations suggest that abnormal control of B-cell maturation in response to polyclonal antigenic stimulation may play a central role in the pathogenesis of ARL. The recent finding of clonal HIV integrated within macrophages in a subset of early lymphomas also provides evidence for abnormalities outside the B-cell compartment playing roles in this disease. Overall, ARLs generally appear to be outgrowths of antigen-driven B-cells with significant growth control influence provided by abnormal T-cell and antigen-presenting cell processes.

Restricted use of VH4 germline segments in an acute multiple sclerosis brain

Multiple sclerosis (MS) cerebrospinal fluid and brain contain increased IgG and oligoclonal bands. Whether this oligoclonal and polyclonal IgG is directed against a disease-relevant antigen remains unknown. To distinguish between random activation versus a targeted B-cell response, we analyzed the IgG heavy chain variable region (VH) repertoire expressed in different lesions of an acute MS brain. To obtain a representative sample of the VH repertoire, we constructed directional complementary DNA libraries from plaque-periplaque messenger RNA and amplified VH regions from the library by nested polymerase chain reaction. When MS VH sequences were aligned to germline segments, about 60% of different VH sequences in the acute MS brain were VH4 germline segments, significantly greater than the known approximately 20% VH4 germline prevalence. Specific VH sequences were overrepresented and expressed at multiple plaque sites. Within some overexpressed populations, there were distinct sequence differences (clonal variants) indicative of clonal expansion. Alignment of VH sequences to their closest germline counterparts revealed extensive somatic mutation and the preferential accumulation of amino acid replacement mutations in complementarity determining regions. These observations suggest the limited B-cell response found in this acute MS brain was antigen driven.

The pathologic significance of the immunoglobulins expressed by chronic lymphocytic leukemia B-cells in the development of autoimmune hemolytic anemia

The increased number of CD5+ B-cells in some human autoimmune diseases, the frequent commitment of CD5+ B-cells to the production of natural autoantibodies, and the apparent involvement of these cells in the pathogenesis of the autoimmune hemolytic anemia (AIHA) in certain mouse models suggests a causal relationship between the CD5+ chronic lymphocytic leukemia (CLL) B-cell and the AIHA which frequently develops in this malignant disorder. In support of this conclusion is our recent finding that the VH region gene repertoire of the leukemic B-cells from CLL patients with AIHA is rather biased and characterised by the over-representation of the 51p1 VH gene. On the other hand, it appears relatively certain that the pathogenic anti-erythrocyte antibodies in CLL patients with AIHA are produced by remnant normal B-cells, and that the antibodies expressed by the leukemic CD5+ B-cells do not directly bind red blood cells (RBC). Of interest, the antibodies produced by the leukemic B-cells from CLL patients with AIHA might have in common rheumatoid factor (RF) activity. These data indicate that the antibodies produced by the leukemic B-cells from CLL patients with AIHA are not directly involved in red blood cell destruction, but may be involved in the induction or amplification of a polyclonal anti-RBC response. Finally, we discuss the possible clinical implications of our finding that CLL patients with leukemic cells expressing the 51p1 VH gene may be at a higher risk to develop autoimmune hemolytic anemia.

Cytotoxicity of murine B lymphocytes induced by human VH4-34 (VH4.21) gene-encoded monoclonal antibodies

We have previously described specific binding and cytotoxicity of human B lymphocytes by VH4-34 gene-derived anti-i cold agglutinin (CA) mAbs. Here we demonstrate that the carbohydrate ligand recognized by human VH4-34 anti-i CA mAbs is also expressed on murine B lymphocytes. Similar to human B cells, binding of murine B lymphocytes by VH4-34-derived anti-i CA mAbs leads to rapid cytotoxicity of target cells as tested both in vitro and in vivo. Moreover, the mechanism leading to murine B cell death is also similar to human B cells, since morphologically identical membrane pores were detected within 15 min of mAb exposure by scanning electron microscopy. The conservation of the carbohydrate ligand across species provides an ideal system to study the function of human VH4-34 gene derived Abs in immune regulation.