Genetic and immunological mechanisms in the pathogenesis of systemic lupus erythematosus

Juvenile systemic lupus erythematosus in multicase families from Saudi Arabia: comparison of clinical and laboratory variables with sporadic cases

The object of this study was to compare patients with familial versus sporadic systemic lupus erythematosus (SLE) with respect to clinical, laboratory variables and outcome. The familial SLE group comprised 12 patients while the comparative group comprised 24 patients selected by systemic sampling from our pediatric rheumatology clinic database. Those patients are listed according to the date of referral, which represents a sampling frame. The first patient was chosen randomly and subsequent patients were chosen at intervals of three. The two groups were compared with respect to: demographic information, age of onset of SLE, disease and follow up duration, clinical and laboratory variables and outcome. The patients from the familial group were younger and had an earlier age of onset of disease ( P 0.03, 0.001 respectively). Seven patients with familial SLE were from the eastern region of Saudi Arabia ( P 0.006). The two groups were comparable with respect to gender, disease duration and follow-up. At diagnosis, the discoid rash was more frequent in the familial group ( P 0.03) while other clinical and laboratory variables including disease activity as measured by SLEDAI did not show significant differences. The mean dose of steroid and use of other immunosuppressive therapy were similar in both groups. Three patients from the familial group died; two of them had unusual complications (one patient had transverse myelitis and pancreatic pesudocyst and the other one had extensive pyoderma gangerunosum). All patients from the sporadic group are alive in stable condition but one patient had severe central nervous system disease. Familial SLE patients tend to be younger and more likely to have discoid rash, in addition a marked difference in the origin of patients was noted. These differences may be helpful in identifying SLE patients with a stronger genetic predisposition. The mortality among familial SLE patients is more frequent which may reflect the disease severity.

Nonsegmental vitiligo and autoimmune mechanism

Nonsegmental vitiligo is a depigmented skin disorder showing acquired, progressive, and depigmented lesions of the skin, mucosa, and hair. It is believed to be caused mainly by the autoimmune loss of melanocytes from the involved areas. It is frequently associated with other autoimmune diseases, particularly autoimmune thyroid diseases including Hashimoto's thyroiditis and Graves' disease, rheumatoid arthritis, type 1 diabetes, psoriasis, pernicious anemia, systemic lupus erythematosus, Addison's disease, and alopecia areata. This indicates the presence of genetically determined susceptibility to not only vitiligo but also to other autoimmune disorders. Here, we summarize current understanding of autoimmune pathogenesis in non-segmental vitiligo.

Cutaneous lupus erythematosus: a review

This article will review and update information about the pathogenesis, clinical presentation, diagnosis, and treatment of cutaneous lupus erythematosus. Lupus erythematosus (LE) can present as a skin eruption, with or without systemic disease. Cutaneous LE is subdivided into chronic cutaneous LE, subacute cutaneous LE and acute LE. The prevalence of systemic lupus erythematosus (SLE) is 17-48/100,000 population worldwide. Skin disease is one of the most frequent clinical complaints of patients suffering from SLE. It has been found to occur in up to 70% of patients during the course of the disease. The most frequent mucocutaneous manifestations of SLE are malar rash (40%), alopecia (24%), and oral ulcers (19%). It has been suggested that risk factors that are more likely to signal transition of cutaneous into systemic LE are high ANA titers (> 1:320) and the presence of arthralgias. CLE patients who exhibit these symptoms should be monitored closely, since they may be at increased risk to develop SLE.

Familial lupus erythematosus. Clinical and immunologic features of 125 multiplex families

Evidence for a genetic susceptibility to systemic lupus erythematosus (SLE) in humans is based on the high concordance rate observed in identical twins and on the relatively high incidence of familial cases. Although recent genetic studies have lead to significant advances in the identification of new susceptibility genes in SLE, no large clinico-pathologic study of familial SLE has been reported to date. In the present study, we describe the main clinical and immunologic features of 125 lupus multiplex families including at least 2 cases of SLE and/or discoid lupus erythematosus (DLE), recruited through a French national survey starting in July 1997. Medical records of all affected members were reviewed by the same investigator, all available family members were interviewed using the same standardized procedure, and blood was drawn for autoantibodies typing. Clinical and immunologic features of 90 probands from multiplex SLE families were compared with those of 100 sporadic SLE patients sharing the same French Caucasian origin. The 125 lupus multiplex families included 282 affected members (2.3 patients per family); of the 125 families, 96 were of French Caucasian origin. One hundred multiplex families included 2 affected relatives, while 25 included 3 or more affected individuals. The relationship between affected members was sibs (45%), parent-offspring (31%), and second-degree (24%). An autosomal dominant mode of inheritance was strongly suggested in 1 extended pedigree with 6 clinically affected members, and a recessive pattern was suspected in 5 other families. No obvious mode of inheritance could be suspected in most of the remainder. Among French Caucasians, sex ratio, mean age at onset, and clinical and biologic SLE-related manifestations were not significantly different in multiplex compared with sporadic SLE cases. The analysis of these 125 multiplex families suggests a genetic heterogeneity that should be considered for ongoing genomic screening.

Overlap of the anti-cardiolipin and anti-nucleosome responses of the (NZW X BXSB)F1 mouse strain: a new pattern of cross-reactivity for lupus-related autoantibodies

The association of anti-nuclear antigen (ANA) and anti-cardiolipin (CL) antibodies is often observed during systemic lupus erythematosus (SLE) or the primary anti-phospholipid syndrome, thereby raising the possibility of a relationship between these two autoantibody populations. To determine whether ANA and anti-CL antibodies can overlap, we derived, from a male (NZW x BXSB)F1 mouse, 14 hybridomas selected based on their capacities to react with CL and to label HEp-2 cell nuclei. Four of these anti-CL were IgG and bound to CL and phosphatidylserine in a cofactor-dependent manner and reacted strongly with nucleosomes. Variable region sequence analysis indicated that these four monoclonal antibodies (mAb) were derived from three independent B cell clones that used recurrent heavy and/or light chain immunoglobulin rearrangements, as assessed by comparison with each other and prototypic anti-CL mAb previously derived from different lupus mouse strains. These results indicate that anti-CL mAb can have overlapping cross-reactivities with nucleosomes, thereby defining a new category of SLE-related autoantibodies characterized by their capacities to recognize distinct supramolecular complexes, formed by the association of an anionic structure and a protein, that exert a strong selective pressure on autoreactive B cell clones.

Long PCR detection of the C4A null allele in B8-C4AQ0-C4B1-DR3

The genes coding for the two components of complement 4 (C4), C4A and C4B, are located within the major histocompatibility complex (MHC) on the short arm of chromosome 6. Several studies have shown that deficiency of C4A is associated with systemic lupus erythematosus (SLE), rheumatoid arthritis and scleroderma. A large deletion covering most of the C4A gene and the 21-hydroxylase-A (21-OHA) pseudogene found on the extended haplotype B8-C4AQ0-C4B1-DR3 is estimated to account for approximately two-thirds of C4A deficiency in Caucasian SLE patients. Detection of this C4A null allele has been technically difficult due to the high degree of homology between C4A and C4B, with protein analysis and restriction fragment length polymorphism (RFLP) analysis using Southern blotting being the only approaches available. In this study, a long PCR strategy was used to rapidly genotype for the C4A deletion through specific primer design. The methodology makes use of the unique sequence of the G11 gene upstream of C4A and the sequence of a 6.4 kb retrotransposon, the human endogenous retrovirus HERV-K(C4), which is present in intron 9 of C4A but absent in the case of the deletion.

MHC class II-bound self peptides from autoimmune MRL/lpr mice reveal potential T cell epitopes for autoantibody production in murine systemic lupus erythematosus

The systemic lupus erythematosus-like syndrome in MRL/lpr mice involves high-titered IgG autoantibodies, particularly antinuclear Abs that target histones, DNA, and RNA particles. Although T cell help is required for the generation of antinuclear Abs, the epitopes recognized by such helper T cells are unknown. To address this question, we isolated and sequenced self peptides bound by MHC class II molecules from MRL/lpr mice. We identified a number of peptides that are not seen in similar preparations from nonautoimmune C3H animals. The "abnormal" peptide donors include histone, a protein component of a small nuclear ribonucleoprotein, ribosomal proteins, and RNA processing enzymes. We postulate that the peptides from these donors are T cell epitopes required for the generation of the most frequent antinuclear Abs specificities seen in MRL/lpr mice.

[Immunogenetic bases of systemic lupus erythematosus in humans]

INTRODUCTION

Systemic lupus erythematosus (SLE) is an autoimmune disease of unknown pathogenesis. Familial studies and concordance rates among affected twins suggest that human SLE has a strong genetic basis.

CURRENT KNOWLEDGE AND KEY POINTS

Recent studies have emphasized that SLE, like other autoimmune diseases, is a complex genetic trait with contributions of both major histocompatibility complex (MHC) associated genes and multiple non-MHC genes. Recent significant advances have been made in the genetic analysis of complex traits, which allow the identification of new candidate genes in SLE. Among the genes reviewed in this article, some polymorphisms of Fc gamma receptor genes and other genes or loci localized on the long arm of the human chromosome 1 appear to be very promising.

FUTURE PROSPECTS AND PROJECTS

The identification of new susceptibility genes in SLE will certainly provide important insights into the breakdown of self-tolerance mechanisms leading to autoimmune diseases. To achieve this objective, the recruitment of a large number of genetic traits of multiplex families presenting with SLE is therefore essential. More than 125 multiplex families have been collected to date in France.

A promoter polymorphism of tumor necrosis factor alpha associated with systemic lupus erythematosus in African-Americans

OBJECTIVE

The polymorphic tumor necrosis factor alpha (TNFalpha) gene encodes a cytokine involved in inflammation, angiogenesis, and apoptosis. One polymorphic variant is associated with increased production of TNFalpha. This study examined the frequency of this polymorphic variant in African-American patients with systemic lupus erythematosus (SLE) compared with controls.

METHODS

We determined the gene frequency of the polymorphic variant of TNFalpha in an African-American SLE patient population and in a geographically matched African-American control population.

RESULTS

The gene frequency of the TNFalpha -308A polymorphism was higher in the African-American SLE population than in the control population. This relationship was independent of major histocompatibility complex DR alleles.

CONCLUSION

The TNFalpha -308A polymorphism is associated with an increased risk of SLE in African-Americans.

Analysis of CD80 and CD86 expression on peripheral blood B lymphocytes reveals increased expression of CD86 in lupus patients

We screened peripheral blood mononuclear cells from 13 SLE patients, all having quiescent disease at the time of analysis, 12 allergy patients, and 21 normal subjects for the expression of CD80 (B7-1) and CD86 (B7-2, B70) on small (resting) and large (activated) subsets of CD19+ B cells. The percentage of CD86+ cells was significantly higher in all B cell subsets in the SLE patients compared to either normal controls or allergy patients. No differences in the mean percentage CD86+ stained B cells (CD19+) were found when comparing the allergy patients and the normal controls. The percentage of CD80+ cells in the large activated B cell (CD19+) subset of the SLE patient population was significantly higher than in the comparable subset from the normal controls and the allergy patients. Comparison of the small resting B cell subset did not reveal a significant difference in CD80 expression between the normal controls, the allergy patients, and the SLE patients. Our findings suggest that the B7 family of molecules, and CD86 in particular, may reflect immunologic dysregulation in patients with autoimmune disease and may reflect a state facilitating heightened B cell activity and hypergammaglobulinemia that occur in active SLE.

Multiple defects in the immune system of Lyn-deficient mice, culminating in autoimmune disease

Mice homozygous for a disruption at the Lyn locus display abnormalities associated with the B lymphocyte lineage and in mast cell function. Despite reduced numbers of recirculating B lymphocytes, Lyn-/- mice are immunoglobulin M (IgM) hyperglobulinemic. Immune responses to T-independent and T-dependent antigens are affected. Lyn-/- mice fail to mediate an allergic response to IgE cross-linking, indicating that activation of LYN plays an indispensable role in Fc epsilon RI signaling. Lyn-/- mice have circulating autoreactive antibodies, and many show severe glomerulonephritis caused by the deposition of IgG immune complexes in the kidney, a pathology reminiscent of systemic lupus erythematosus. Collectively, these results implicate LYN as having an indispensable role in immunoglobulin-mediated signaling, particularly in establishing B cell tolerance.

Unexpectedly high occurrence of catalytic antibodies in MRL/lpr and SJL mice immunized with a transition-state analog: is there a linkage to autoimmunity?

Upon testing the ability of several strains of mice to elicit esterolytic antibodies after immunization with a p-nitrobenzyl phosphonate hapten, we have found that the occurrence of catalytic antibodies in SJL and MRL/lpr autoimmune mice is dramatically higher than in normal mouse strains (e.g., the wild-type MRL/++ or BALB/c). Fewer than 10 catalytic clones are usually obtained from a single fusion of lymphocytes taken from normal mice, whereas several hundred catalytic clones are obtained in SJL or MRL/lpr mice. Differences in the numbers of hapten-binding clones do not account for the high occurrences of catalytic clones in these strains. This phenomenon prevailed in the early responses; in both SJL and MRL/lpr mice a significant decline in the appearance of catalytic clones was observed after multiple immunizations. Esterolytic antibodies were not found in MRL/lpr mice immunized with haptens that do not mimic the transition state for the hydrolysis of the ester substrate (e.g., with a substrate analog). The catalytic antibodies manifest high specificity to the antigen and variability in their binding and catalytic properties. The use of autoimmunity-prone mice may greatly expand the repertoire of catalytic clones elicited against a transition-state analog hapten. More intriguing is the possible linkage between autoimmunity and the appearance of catalytic antibodies. These results suggest that there is normally a selection against the expression of certain variable genes encoding antibodies with catalytic activity.

Restricted junctional diversity of T cell receptor delta gene rearrangements expressed in systemic lupus erythematosus (SLE) patients

SLE is an autoimmune connective tissue disorder affecting multiple organs, in which T cells may play a central role. This study investigated T cell receptor (TCR) gamma/delta repertoire expression in peripheral blood mononuclear cells (PBMC) of SLE patients and healthy individuals using variable (V) gene family-specific polymerase chain reaction (PCR) amplification of TCR cDNA. The expressed V gamma repertoires were diverse in SLE and control PBMC, although V gamma IV gene rearrangements were barely detectable or not expressed in some patients. In contrast, delta chain expression was limited in all SLE patients, with delta transcripts rearranged primarily to the V delta 1 and V delta 2 genes, as opposed to control PBMC, in which all six V delta genes were detected. To assess the clonality of TCR populations, cDNA clones containing rearranged V delta 1, V delta 2 and V gamma 9 transcripts were sequenced from PBMC of both patients and controls. For controls, delta chain junctional region sequences showed extensive molecular heterogeneity, since virtually all 34 V delta 1 and 32 V delta 2 cDNA clones analysed were unique. A few V gamma 9 cDNA clones (3/21) had the same junctional region sequence motif (EVQEL) encoded largely by the V gamma 9 and joining (J) gamma P gene segments. Identical V gamma 9 junctional sequences were found in SLE patients that did not contain the EVQEL motif present in normal peripheral blood gamma/delta lymphocytes. Moreover, the predominant V delta 1-J delta -constant (C) delta and V delta 2-J delta-C delta gene rearrangements expressed in SLE PBMC showed restricted junctional diversity, but the oligoclonal delta transcripts were different in each patient. These findings suggest in vivo oligoclonal expansion of gamma/delta T cells in the periphery of SLE patients in response to a limited number of nominal ligands. Whether gamma/delta T cells contribute to the development of systemic autoimmunity remains to be investigated.

T cell repertoire and autoimmune diseases

Self-reactivity and autoimmunity are processes related to the breakage of self-tolerance that can be distinguished by their different clinical outcome and are widely accepted cornerstones of immunology. The finding that several potentially autoaggressive cells contribute to the repertoire of healthy individuals has stimulated a great deal of experimental work aimed at understanding the mechanisms that prevent autoimmune pathology. In this review we will consider the basic principles, and our present knowledge of the rules that preside over the interplay of the immune system with self-components. One viewpoint stresses the importance of major histocompatibility complex (MHC) and non-MHC genes in determining genetic predisposition to develop autoimmune phenomena. At a different level there is a strong interest in understanding the mechanisms of processing and presentation of self antigens, especially during ontogeny. Another topic of major interest concerns the interaction between MHC genes and the T cell receptor (TcR) complex as well as the identification of TcR V genes that are preferentially expressed by autoimmune T cells. All of these aspects are evaluated in the context of tolerance based on deletion and anergy. Finally we will propose a general model of autoimmunity based on the most recent findings concerning the biological activity of exogenous superantigens.