Regulatory T cells as central regulators of both autoimmunity and B cell malignancy in New Zealand Black mice

NKG2D+CD4+ T Cells Kill Regulatory T Cells in a NKG2D-NKG2D Ligand- Dependent Manner in Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE) features a decreased pool of CD4⁺CD25⁺Foxp3⁺ T regulatory (Treg) cells. We had previously observed NKG2D⁺CD4⁺ T cell expansion in contrast to a decreased pool of Treg cells in SLE patients, but whether NKG2D⁺CD4⁺ T cells contribute to the decreased Treg cells remains unclear. In the present study, we found that the NKG2D⁺CD4⁺ T cells efficiently killed NKG2D ligand (NKG2DL)⁺ Treg cells in vitro, whereby the surviving Treg cells in SLE patients showed no detectable expression of NKG2DLs. It was further found that MRL/lpr lupus mice have significantly increased percentage of NKG2D⁺CD4⁺ T cells and obvious decreased percentage of Treg cells, as compared with wild-type mice. Adoptively transferred NKG2DL⁺ Treg cells were found to be efficiently killed in MRL/lpr lupus mice, with NKG2D neutralization remarkably attenuating this killing. Anti-NKG2D or anti-interferon-alpha receptor (IFNAR) antibodies treatment in MRL/lpr mice restored Treg cells numbers and markedly ameliorated the lupus disease. These results suggest that NKG2D⁺CD4⁺ T cells are involved in the pathogenesis of SLE by killing Treg cells in a NKG2D-NKG2DL-dependent manner. Targeting the NKG2D-NKG2DL interaction might be a potential therapeutic strategy by which Treg cells can be protected from cytolysis in SLE patients.

Women and primary biliary cirrhosis

Primary biliary cirrhosis occurs more frequently in women, and previous studies indicated that the average age of primary biliary cirrhosis (PBC) onset makes pregnancy in PBC patients uncommon. However, more recently, improved diagnostic testing has enabled detection of PBC in younger women, including those of childbearing age. This has led investigators to become increasingly interested in the relationship between the ontogeny of PBC and pregnancy. Published cases indicate that the typical age for pregnant women to be diagnosed with PBC is in the early 30s, and that during gestation, pruritus and jaundice are the most common symptoms. During gestation, susceptible women may experience onset of PBC resulting from the drastic changes in female hormones; this would include not only the mitochondrial damage due to accumulation of bile acids but also changes in the immune response during the different stages of pregnancy that might play an important role in the breakdown of self-tolerance. The mechanisms underlying the potential relationship between PBC and pregnancy warrant further investigation. For women first diagnosed with PBC during gestation, or those for whom first appearance of a flare up occurs during and postpartum, investigation of the immune response throughout gestation could provide new avenues for immunologic therapeutic intervention and the discovery of new treatment strategies for PBC.

Antigens in chronic lymphocytic leukemia--implications for cell origin and leukemogenesis

Several types of B cell tumors, particularly MALT lymphomas, are known to have an antigen-driven component in tumor development. Over the past two decades substantial data have accumulated regarding the restricted immunoglobulin (IG) gene repertoire in chronic lymphocytic leukemia (CLL) and its potential implications for antigenic drive in the disease development and progression. Herein we discuss how evidence first illustrated a link between certain B cell receptor (BCR) specificities and disease outcome and the subsequent large-scale IG analyses which revealed the extent of "stereotyped" BCRs in CLL. More recent studies on CLL antibody reactivity have gradually provided clues as to which antigens may be involved in the tumor development. Significantly, CLL monoclonal antibodies have been shown to resemble natural antibodies recognizing molecular motifs both on apoptotic cells (e.g. modified cytoskeletal proteins and oxidation-specific epitopes), as well as exogenous bacteria, indicating that CLL clones possibly arise from B cells which have dual function as scavengers of apoptotic debris, while also having the ability to bind conserved bacterial cell structures. Such revelations have led us to re-evaluate both the phenotypic and functional characteristics of the tumor B cells and the pathway by which CLL arises and develops.

Interferon-alpha regulates the dynamic balance between human activated regulatory and effector T cells: implications for antiviral and autoimmune responses

An adequate effector response against pathogens and its subsequent inactivation after pathogen clearance are critical for the maintenance of immune homeostasis. This process involves an initial phase of T-cell effector (Teff) activation followed by the expansion of regulatory T cells (Tregs), a unique cell population that limits Teff functions. However, significant questions remain unanswered about the mechanisms that regulate the balance between these cell populations. Using an in vitro system to mimic T-cell activation in human peripheral blood mononuclear cells (PBMC), we analysed the patterns of Treg and Teff activation, with special attention to the role of type I interferon (IFN-I). Interestingly, we found that IFN-alpha, either exogenously added or endogenously induced, suppressed the generation of CD4(+) FoxP3(HI )IFN-gamma(Neg) activated Tregs (aTregs) while simultaneously promoting propagation of CD4(+) FoxP3(Low/Neg )IFN-gamma(Pos) activated Teffs (aTeffs). We also showed that IFN-alpha-mediated inhibition of interleukin (IL)-2 production may play an essential role in IFN-alpha-induced suppression of aTregs. In order to test our findings in a disease state with chronically elevated IFN-alpha, we investigated systemic lupus erythematosus (SLE). Plasma from patients with SLE was found to contain IFN-I activity that suppressed aTreg generation. Furthermore, anti-CD3 activated SLE PBMCs exhibited preferential expansion of aTeffs with a very limited increase in aTreg numbers. Together, these observations support a model whereby a transient production of IFN-alpha (such as is seen in an early antiviral response) may promote CD4 effector functions by delaying aTreg generation, but a chronic elevation of IFN-alpha may tip the aTeff:aTreg balance towards aTeffs and autoimmunity.

Murine models of autoimmune cholangitis

PURPOSE OF REVIEW

Primary biliary cirrhosis (PBC) is a human autoimmune liver disease whose molecular pathogenesis is poorly understood because of the difficulty in accessing human tissue and the absence of appropriate animal models. Recently, several unique murine models of human PBC have been discovered. These models have great potential for illustrating the cause and the cellular events that lead to biliary-specific damage. The purpose of this review is to summarize recent progress in these models.

RECENT FINDINGS

The murine models of autoimmune cholangitis include the transforming growth factor beta receptor II (TGF-betaRII) dominant-negative (dnTGF-betaRII), IL-2 receptor alpha deleted (IL-2Ralpha-/-), scurfy, nonobese diabetic (NOD) c3c4, and Ae2 gene-disrupted (Ae2a,b-/-) mice. Recently, we have also established a successful murine model following the immunization with a chemical mimicry of the lipoyl-lysine residue of the E2 component of PDC-E2.

SUMMARY

These emerging murine models have greatly enabled researchers to address the pathogenesis of human PBC and to elucidate pathogenic factors. These models will ultimately lead to new therapeutic options for human PBC.

Experimental evidence on the immunopathogenesis of primary biliary cirrhosis

Primary biliary cirrhosis (PBC) is a chronic cholestatic liver disease for which an autoimmune pathogenesis is supported by clinical and experimental data, including the presence of autoantibodies and autoreactive T cells. The etiology remains to be determined, yet data suggest that both a susceptible genetic background and unknown environmental factors determine disease onset. Multiple infectious and chemical candidates have been proposed to trigger the disease in a genetically susceptible host, mostly by molecular mimicry. Most recently, several murine models have been reported, including genetically determined models as well as models induced by immunization with xenobiotics and bacteria.

Gene therapy in autoimmune diseases: challenges and opportunities

Clinical treatment of autoimmune disorders presents a special challenge. For decades, most clinical regimens in autoimmunity has been largely symptomatic and non-disease specific. Although data from vigorous research has lead to accumulating knowledge on the pathogenic and immunological mechanisms of many autoimmune diseases, their direct clinical applications have been sparse. Advances in biotechnology have laid the groundwork for potent and specific molecular targeting therapies by gene therapy, and have just begun to be investigated in the treatment of autoimmune disorders. Such work has been largely based on the availability of well-established animal models of common autoimmune disorders, and the efficacy of strategic approaches initially investigated and validated in these models. Although these preclinical animal model studies have provided the proof-of-concept for multiple potential applications, human clinical trials on gene therapy in autoimmunity are still at its infancy. The recent success of Phase I/II clinical trials of gene therapy in rheumatoid arthritis and multiple sclerosis, development of cutting edge technology in target identification, as well as gene delivery systems have now set the stage for a more thorough and vigorous pace in the near future to advance this exciting field.

Incidence and nature of infectious disease in patients treated with anti-TNF agents

Tumor necrosis factor alpha (TNF-alpha) inhibitors offer a targeted therapeutic strategy that contrasts with the nonspecific immunosuppressive agents traditionally used to treat most inflammatory diseases. These biologic agents have had a significant impact in ameliorating the signs and symptoms of inflammatory rheumatoid disease and improving patient function. From the onset of clinical trials, a central concern of cytokine blockade has been a potential increase in susceptibility to infections. Not surprisingly, a variety of infections have been reported in association with the use of TNF-alpha inhibitor agents. In particular, there is evidence suggesting an increased rate of granulomatous infections in patients treated with monoclonal TNF-alpha inhibitors. This review provides the incidence and nature of infections in patients treated with TNF-alpha inhibitor agents and reminds the clinician of the required vigilance in monitoring patients.