Alterations in the stoichiometric balance between members of Bcl-2 and Fas apoptotic pathway could lead to the pathogenesis of systemic lupus erythematosus (SLE). We showed that patients with SLE displayed increased expression in antiapoptotic members of the Bcl-2 and Fas apoptotic pathways in isolated mononuclear cells. Further, mice (Bcl2l11(-/-)Fas(lpr/lpr)) lacking the Bcl-2 pro-apoptotic member, Bim (Bcl2l11(-/-)) and and with an lpr mutation in the gene encoding Fas (Fas(lpr/lpr)) developed severe SLE-like disease by 16 weeks of age unlike Bcl2l11(-/-) or Fas(lpr/lpr) mice. Bcl2l11(-/-)Fas(lpr/lpr) antigen-presenting cells (APCs) were markedly activated, and their numbers were increased in lymphoid tissues and in kidneys, yet numerous TUNEL-positive cells were observed in glomeruli of Bcl2l11(-/-)Fas(lpr/lpr) mice. These data demonstrate that dysregulation of the Bcl-2 or Fas pathways can alter the function of APCs, thereby leading to SLE pathogenesis.

Systemic lupus erythematosus (SLE) is a chronic autoimmune disease that is characterized by defective immune tolerance combined with immune cell hyperactivity resulting in the production of pathogenic autoantibodies. Previous gene expression studies employing whole blood or peripheral blood mononuclear cells (PBMC) have demonstrated that a majority of patients with active disease have increased expression of type I interferon (IFN) inducible transcripts known as the IFN signature. The goal of the current study was to assess the gene expression profiles of isolated leukocyte subsets obtained from SLE patients. Subsets including CD19+ B lymphocytes, CD3+CD4+ T lymphocytes and CD33+ myeloid cells were simultaneously sorted from PBMC. The SLE transcriptomes were assessed for differentially expressed genes as compared to healthy controls. SLE CD33+ myeloid cells exhibited the greatest number of differentially expressed genes at 208 transcripts, SLE B cells expressed 174 transcripts and SLE CD3+CD4+ T cells expressed 92 transcripts. Only 4.4% (21) of the 474 total transcripts, many associated with the IFN signature, were shared by all three subsets. Transcriptional profiles translated into increased protein expression for CD38, CD63, CD107a and CD169. Moreover, these studies demonstrated that both SLE lymphoid and myeloid subsets expressed elevated transcripts for cytosolic RNA and DNA sensors and downstream effectors mediating IFN and cytokine production. Prolonged upregulation of nucleic acid sensing pathways could modulate immune effector functions and initiate or contribute to the systemic inflammation observed in SLE.

Objective. Interleukin‐10 (IL‐10) has been shown to exert both antiinflammatory and immunostimulatory effects in vivo and in vitro. We therefore sought to examine the role of this cytokine in rheumatoid arthritis (RA) by assessing serum and synovial fluid IL‐10 levels. Methods. Serum and synovial fluid samples were collected from patients with RA and patients with various inflammatory, infectious, and noninflammatory arthritides (controls). IL‐10 was assayed using an IL‐10‐specific enzyme‐linked immunosorbent assay, and messenger RNA (mRNA) levels were assessed by semi‐quantitative polymerase chain reaction (PCR) techniques. Results.Both RA serum and synovial fluid contained significantly elevated IL‐10 levels compared with levels in normal subjects or in control patients (P < 0.01). Some patients with spondylarthropathy also manifested increased serum levels of IL‐10. Serum levels of IL‐10 did not correlate with standard measures of clinical activity, but were shown to correlate significantly with serum rheumatoid factor (RF) titers and in vitro levels of spontaneous IgM‐RF production (P < 0.05). PCR analyses demonstrated the constitutive expression of IL‐10 mRNA by the non–T cell population, and semiquantitative PCR analysis documented elevated levels of IL‐10 mRNA in circulating mononuclear cells of those RA patients who were not treated with slow‐acting antirheumatic drugs. Analysis of IL‐10 mRNA revealed the cytokine to be of human, and not viral, origin. Conclusion. These data suggest that there is increased production of IL‐10 by non‐T cells in patients with RA. This may contribute to the diminished T cell function and increased antibody and RF production in these patients.

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SLE is a chronic autoimmune disease caused by perturbations of the immune system. The clinical presentation is heterogeneous, largely because of the multiple genetic and environmental factors that contribute to disease initiation and progression. Over the last 60 years, there have been a number of significant leaps in our understanding of the immunological mechanisms driving disease processes. We now know that multiple leucocyte subsets, together with inflammatory cytokines, chemokines and regulatory mediators that are normally involved in host protection from invading pathogens, contribute to the inflammatory events leading to tissue destruction and organ failure. In this broad overview, we discuss the main pathways involved in SLE and highlight new findings. We describe the immunological changes that characterize this form of autoimmunity. The major leucocytes that are essential for disease progression are discussed, together with key mediators that propagate the immune response and drive the inflammatory response in SLE.

Though B cells play key roles in lupus pathogenesis, the molecular circuitry and its dysregulation in these cells as disease evolves remain poorly understood. To address this, a comprehensive scan of multiple signaling axes using multiplexed Western blotting was undertaken in several different murine lupus strains. PI3K/AKT/ mTOR (mTOR, mammalian target of rapamycin), MEK1/Erk1/2, p38, NF-κB, multiple Bcl-2 family members, and cell-cycle molecules were observed to be hyperexpressed in lupus B cells in an age-dependent and lupus susceptibility gene-dose-dependent manner. Therapeutic targeting of the AKT/mTOR axis using a rapamycin (sirolimus) derivative ameliorated the serological, cellular, and pathological phenotypes associated with lupus. Surprisingly, the targeting of this axis was associated with the crippling of several other signaling axes. These studies reveal that lupus pathogenesis is contingent upon the activation of an elaborate network of signaling cascades that is shared among genetically distinct mouse models and raise hope that targeting pivotal nodes in these networks may offer therapeutic benefit.

Recent evidence suggests that B and T cell interactions may be paramount in relapsing remitting multiple sclerosis (RRMS) disease pathogenesis. We hypothesized that memory B cell pools from RRMS patients may specifically harbor a subset of potent neuro-antigen presenting cells that support neuro-antigen reactive T cell proliferation and cytokine secretion. To test this hypothesis, we compared CD80 and HLA-DR expression, IL-10 and LTα secretion, neuro-antigen binding capacity, and neuro-antigen presentation by memory B cells from RRMS patients to naïve B cells from RRMS patients and to memory and naïve B cells from healthy donors (HD). We identified memory B cells from some RRMS patients that elicited CD4+ T cell proliferation and IFN-γ secretion in response to myelin basic protein (MBP) and myelin oligodendrocyte glycoprotein (MOG). Notwithstanding the fact that the phenotypic parameters that promote efficient antigen presentation were observed to be similar between RRMS and HD memory B cells, a corresponding capability to elicit CD4+ T cell proliferation in response to MBP and MOG was not observed in HD memory B cells. Our results demonstrate for the first time that the memory B cell pool in RRMS harbors neuro-antigen specific B cells that can activate T cells.

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