In vitro induction of IgG anti-DNA antibody from high density B cells of systemic lupus erythematosus patients by an HLA DR-restricted T cell clone

Association between vitamin D, oestradiol and interferon-gamma in female patients with inactive systemic lupus erythematosus: A cross-sectional study

Objectives

To investigate possible associations between 25-hydroxyvitamin D₃ (25(OH)D₃), oestradiol (E₂) and IFN-gamma (IFNγ) in female patients with inactive systemic lupus erythematosus (SLE).

Methods

Female patients with inactive SLE and age-matched healthy controls were recruited into this cross-sectional study. Serum concentrations of 25(OH)D_3, E₂ and IFNγ were measured by radioimmunoassay with gamma-counters and enzyme-linked immunosorbent assay.

Results

36 patients and 37 controls were enrolled. In patients with SLE, the concentration of 25(OH)D₃ was lower and E₂ was higher compared with controls. In vitamin D deficient (i.e., 25(OH)D₃≤20 ng/ml) patients, IFNγ was 150% higher compared with patients with 25(OH)D₃>20 ng/ml and controls. The concentration of E₂ was higher in all patients compared with controls independently of the vitamin D level. A difference was found between patients and controls in the correlation of 25(OH)D₃ with E₂ and a positive correlation was found between E₂ and IFNγ in all participants.

Conclusions

Our results suggest that E₂ may have a strong modulating effect on vitamin D function which is significant only at low concentration of E₂.

Apoptosis and systemic lupus erythematosus

Reduced clearance of dying cells by macrophages or increased apoptosis provokes accumulation of cellular fragments in various tissues. This process seems to induce the uptake of autoantigens from apoptotic nuclei or chromatin by dendritic cells (DCs). Then, the DCs present altered self-epitopes to naive T cells. Thus, autoreactive T cells are activated accidentally and may now provide T-cell help for B cells that present peptides processed from secondary necrotic/late apoptotic prey. Impaired phagocytic removal of early apoptotic cells may cause accumulation of secondary necrotic cells and debris in the germinal centers of secondary lymph organs. The latter bind complement and can, therefore, be trapped on the surfaces of follicular DCs (FDCs). B cells may get in contact with intracellular autoantigens that had been released during late stages of apoptotic cell death and are immobilized by FDCs. Consecutively, B cells that had, for example, gained specificity for nuclear auto-antigens during random somatic mutations can receive a short-term survival signal. After migration into the mantle zone, these autoreactive B cells may finally be activated by autoreactive CD4+ T helper cells. B cells then differentiate into memory or plasma cells. The plasma cells produce those pathogenic nuclear autoantibodies. Many defects are known with respect to the clearance of apoptotic cells and cell material, especially that of nuclear origin. Reflecting on the plethora of defects of clearance of apoptotic material already demonstrated in systemic lupus erythematosus, it is reasonable to argue that, for many patients, failure of clearance is at the heart of their disease.

A model B-cell superantigen and the immunobiology of B lymphocytes

Recent reports have shown that protein A of Staphylococcus aureus (SpA) is a specific toxin for B cells by virtue of specific binding interactions with conserved sites on the V(H) region of the B-cell antigen receptor. The structural basis for these Fab-binding interactions has recently been revealed in crystallographic analyses, which have demonstrated many similarities with the interactions of T-cell superantigens. Investigations of the in vivo response to SpA have illustrated how a B-cell superantigen can be used to provide a window for examining fundamental principles that underlie the immunobiology of B lymphocytes.

Thymic microenvironment and NZB mice: the abnormal thymic microenvironment of New Zealand mice correlates with immunopathology

There are distinct microenvironmental abnormalities of thymic architecture in several murine models of SLE defined using immunohistochemistry and a panel of mAb dissected at thymic epithelial markers. To address the issue of the relationship between the thymic microenvironment and autoimmunity, we studied backcross (NZB x NZW) F1 x NZW mice in which 50% of offspring develop nephritis associated with proteinuria and anti-DNA antibodies. We reasoned that if thymic abnormalities are associated with development of disease, the correlation of abnormalities with lupus-like disease in individual backcross mice will form the foundation for identification of the mechanisms involved. In parallel, we directed a genetic linkage analysis, using markers previously shown to be linked to nephritis and IgG autoantibody production, to determine if such loci were similarly associated with microenvironmental changes. Our data demonstrate that all (NZB x NZW) F1 x NZW backcross mice with disease have microenvironmental defects. Although the microenvironmental defects are not sufficient for development of autoimmune disease, the severity of thymic abnormalities correlates with titers of IgG autoantibodies to DNA and with proteinuria. Consistent with past studies of (NZB x NZW) F1 x NZW mice, genetic markers on proximal chromosome 17 (near MHC) and distal chromosome 4 showed trends for linkage with nephritis. Although the markers chosen only covered about 10-15% of the genome, the results demonstrated trends for linkage with thymic medullary abnormalities for loci on distal chromosome 4 and distal chromosome 1. We believe it will be important to define the biochemical nature of the molecules recognized by these mAbs to understand the relationships between thymic architecture and immunopathology.

Functional activation of lymphocyte CD44 in peripheral blood is a marker of autoimmune disease activity

Interactions between complementary receptors on leukocytes and endothelial cells play a central role in regulating extravasation from the blood and thereby affect both normal and pathologic inflammatory responses. CD44 on lymphocytes that has been "activated" to bind its principal ligand hyaluronate (HA) on endothelium can mediate the primary adhesion (rolling) of lymphocytes to vascular endothelial cells under conditions of physiologic shear stress, and this interaction is used for activated T cell extravasation into an inflamed site in vivo in mice (DeGrendele, H.C., P. Estess, L.J. Picker, and M.H. Siegelman. 1996. J. Exp. Med. 183:1119-1130. DeGrendele, H.D., P. Estess, and M.H. Siegelman. 1997. Science. 278:672-675. DeGrendele, H.C., P. Estess, and M.H. Siegelman. 1997. J. Immunol. 159: 2549-2553). Here, we have investigated the role of lymphocyte-borne-activated CD44 in the human and show that CD44-dependent primary adhesion is induced in human peripheral blood T cells through T cell receptor triggering. In addition, lymphocytes capable of CD44/HA-dependent rolling interactions can be found resident within inflamed tonsils. In analysis of peripheral bloods of patients from a pediatric rheumatology clinic, examining systemic lupus erythematosus, and a group of chronic arthropathies, expression of CD44-dependent primary adhesion strongly correlates with concurrent symptomatic disease, with 85% of samples from clinically active patients showing elevated levels of rolling activity (compared with only 4% of inactive patients). These rolling interactions are predominantly mediated by T cells. The results suggest that circulating T lymphocytes bearing activated CD44 are elevated under conditions of chronic inflammation and that these may represent a pathogenically important subpopulation of activated circulating cells that may provide a reliable marker for autoimmune or chronic inflammatory disease activity.

T cell receptor clonotypes in skin lesions from patients with systemic lupus erythematosus

Systemic lupus erythematosus is an autoimmune disease characterized by the presence of autoantibodies and by lymphocytic infiltration into lesions at several sites such as skin, kidney, and other organs. Immunohistologic studies have clarified that the majority of lymphocytes in the skin are CD4+ alphabeta T cells. In the present work, to clarify the pathologic role of T cells in the skin of systemic lupus erythematosus patients, we analyzed T cell receptor (TCR) clonotypes of T cells infiltrating into skin lesions. TCR Vbeta gene transcripts from T cells from discoid lesions of the skin and peripheral blood lymphocytes of four systemic lupus erythematosus patients were amplified by reverse transcriptase polymerase chain reaction. Southern blot analysis of polymerase chain reaction product demonstrated the heterogeneous TCR Vbeta repertoire of T cells in the skin of systemic lupus erythematosus. Single-strand conformation polymorphism analysis showed several distinct bands for smears of most TCR Vbeta genes from T cells infiltrating the skin, whereas smears with few bands were found for all TCR Vbeta genes from peripheral blood lymphocytes of the same patients. The number of bands encoding each TCR Vbeta gene from the skin was significantly higher compared with peripheral blood lymphocytes. Sequencing analysis showed a Leucine-X-Glycine amino acid motif at position 96-98 in the CDR3 region at the frequency of 23-24% in skin-accumulated T cells from two patients, whereas the frequency of this motif in peripheral T cells was only 0-3%, indicating limited T cell epitopes. In conclusion, T cells infiltrating into the skin of systemic lupus erythematosus patients might recognize restricted T cell epitopes on autoantigens and trigger the autoimmune reaction in skin lesions.

Detection of restricted junctional diversity of peripheral T cells in SLE patients by spectratyping

Analysis of somatic mutations revealed that anti-double-stranded DNA (dsDNA) autoantibodies from patients with systemic lupus erythematosus (SLE) share features of a T cell dependent, antigen driven immune response. Therefore we analysed the length diversity of the complementarity determining region 3 (CDR3) of T cell receptor (TCR) by high resolution gel electrophoresis of 16 V beta family specific RT PCR products (spectratyping). To enable statistical analysis we developed a quantitative scoring method for the histograms. We investigated 16 V beta gene families in peripheral T cells of SLE patients (n = 9) with active (n = 5) and inactive (n = 4) disease as well as normal healthy blood donors (NHD; n = 9). Analysis of TCR V beta spectratypes (active SLE, n = 59; inactive SLE, n = 51 and NHD n = 97) revealed statistically significant differences of CDR3 length distribution between SLE patients and NHD (P < 0.0001 (active SLE/NHD) and P = 0.0034 (inactive SLE/NHD). These results suggest that spectratyping is able to detect clonal activation of peripheral T cells which correlates to disease activity in SLE patients. We conclude that peripheral T cells from SLE patients display features of a secondary antigen driven immune response.

Testosterone suppresses anti-DNA antibody production in peripheral blood mononuclear cells from patients with systemic lupus erythematosus

OBJECTIVE

To study the in vitro effect of testosterone on anti-DNA antibody production in peripheral blood mononuclear cells (PBMC) from patients with systemic lupus erythematosus (SLE) in order to elucidate its regulatory role in SLE.

METHODS

PBMC from SLE patients were cultured with testosterone. IgG anti-double-stranded DNA (anti-dsDNA) antibody, total IgG, and cytokine activity in the supernatants were measured by enzyme-linked immunosorbent assay.

RESULTS

Testosterone suppressed both IgG anti-dsDNA antibody and total IgG production in PBMC from SLE patients. Antibody production in B cells was also suppressed by testosterone, although the magnitude of its effect on B cells was lower than that on PBMC. Interleukin-6 (IL-6) partially restored the testosterone-induced decrease in antibody levels in PBMC. Testosterone reduced IL-6 production in monocytes.

CONCLUSION

These results suggest that testosterone may directly suppress anti-DNA antibody production in PBMC from SLE patients by inhibiting B cell hyperactivity and, indirectly, by down-regulating IL-6 production in monocytes. These results support the therapeutic effects of testosterone on SLE.

Involvement of B-1 cells in mucosal immunity and autoimmunity

B-1 cells are distinguished from conventional B cells by their anatomical localization, surface phenotypes and functional characteristics. The physiological functions and pathological roles of these cells remain controversial. In this review, Masao Murakami and Tasuku Honjo summarize recent evidence for the involvement of B-1 cells in mucosal immunity and autoimmunity, and discuss the relationship between these phenomena.

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.

Cationic and high affinity serum IgG anti-dsDNA antibodies in active lupus nephritis

To investigate differences between cationic anti-dsDNA antibodies during active and inactive nephritis, low- and high-affinity IgG anti-dsDNA antibodies were prepared from sera of a lupus patient and compared for their binding affinity, spectrotype, and idiotype expression. The ratio of high-affinity to low-affinity anti-DNA antibodies and the relative avidity of the high-affinity anti-DNA antibodies decreased when active nephritis became inactive. Isoelectric focusing showed that cationic anti-dsDNA populations were present predominantly in the high-affinity fraction during active nephritis and in the low-affinity fraction during inactive nephritis. Idiotypic analysis by ELISA and Western blotting showed that the high-affinity cationic anti-DNA antibodies during active nephritis were idiotypically different from their low-affinity counterparts during inactive nephritis. The differences in binding affinity and idiotypy of the cationic anti-dsDNA antibodies suggest that certain serum IgG anti-dsDNA antibodies with both cationic charge and high affinity may be associated with active nephritis.

A calreticulin-like protein co-purifies with a '60 kD' component of Ro/SSA, but is not recognized by antibodies in Sjögren's syndrome sera

In this study, we used human tonsils for the isolation of the 60 kD component of the Ro/SSA autoantigen, following the method described by Wu et al. (J Immunol Methods 1989; 121:219-24). Western blot analyses were carried out using Ro/SSA-reactive human Sjögren's syndrome sera, to follow the autoantigen through the purification procedure. A 60 kD Ro/SSA component was eluted as a broad peak from a Mono Q column. Within this peak, a much more abundant protein, co-migrating with the Ro/SSA component on SDS-PAGE, was also eluted. The more abundant protein was further purified on a Superose 12 column and its N-terminal sequence was shown to be identical to that of human calreticulin. The 60 kD Ro/SSA autoantigen was also further purified on the Superose 12 column and was eluted as an asymmetric peak, with the majority being eluted at a position corresponding to 60 kD, whereas the calreticulin-like protein was eluted from the same column as an apparent dimer of approximately 120 kD. A panel of five Ro/SSA-reactive human sera reacted with the purified Ro/SSA antigen, but not with the calreticulin-like protein. Therefore, it is clear that the calreticulin-like protein is not a Ro autoantigen and is distinct from the 60 kD Ro/SSA antigen. As the calreticulin-like protein is a much more abundant protein than the 60 kD Ro/SSA component, its co-purification with the autoantigen on ion-exchange and its close migration with the autoantigen on SDS-PAGE may explain why peptide sequences for human calreticulin were derived from apparent 60 kD Ro/SSA antigen preparations.

B cell activation in clinically quiescent systemic lupus erythematosus (SLE) is related to immunoglobulin levels, but not to levels of anti-dsDNA, nor to concurrent T cell activation

In clinically quiescent SLE hypergammaglobulinaemia, presence of autoantibodies, and increased soluble IL-2 receptors (sIL-2R) have been reported, suggesting persistent B as well as T cell activation. In contrast, the primary immune response to test antigens is markedly decreased. To analyse these phenomena at a cellular level, we undertook a cross-sectional study on 13 non-active SLE patients and 15 controls. We determined the composition of lymphocyte subsets with special attention to activation markers (CD25, HLA-DR, CD38) and the presence of naive T cells (CD45RO-), and related those findings to serological parameters. In non-active SLE patients the expression of activation markers on B cells and T cells was higher than in normal controls (P < or = 0.02), but was not interrelated. Percentages of activated B cells in SLE were related to levels of total IgG (P < 0.02) and IgM (P < 0.02) but not to anti-dsDNA, suggesting a disordered immune system also in clinically quiescent SLE. Numbers of CD4+ cells (P < 0.001) and CD4+CD45RO- cells (P < 0.05) were decreased. The latter finding might explain the anergy to primary test antigens in clinically quiescent SLE.