New Zealand Black Mice Research Articles

The Lupus Susceptibility Locus Sgp3 Encodes the Suppressor of Endogenous Retrovirus Expression SNERV

Elevated endogenous retrovirus (ERV) transcription and anti-ERV antibody reactivity are implicated in lupus pathogenesis. Overproduction of non-ecotropic ERV (NEERV) envelope glycoprotein gp70 and resultant nephritis occur in lupus-prone mice, but whether NEERV mis-expression contributes to lupus etiology is unclear. Here we identified suppressor of NEERV (Snerv) 1 and 2, Krüppel-associated box zinc-finger proteins (KRAB-ZFPs) that repressed NEERV by binding the NEERV long terminal repeat to recruit the transcriptional regulator KAP1. Germline Snerv1/Snerv2 deletion increased activating chromatin modifications, transcription, and gp70 expression from NEERV loci. F1 crosses of lupus-prone New Zealand Black (NZB) and 129 mice to Snerv1/Snerv2-/- mice failed to restore NEERV repression, demonstrating that loss of SNERV underlies the lupus autoantigen gp70 overproduction that promotes nephritis in susceptible mice and that SNERV encodes for Sgp3 (in NZB mice) and Gv-1 loci (in 129 mice). Increased ERV expression in lupus patients inversely correlated with three putative ERV-suppressing KRAB-ZFPs, suggesting that loss of KRAB-ZFP-mediated ERV control may contribute to human lupus pathogenesis.

Compromised NLRP3 and AIM2 inflammasome function in autoimmune NZB/W F1 mouse macrophages.

Inflammasomes are protein complexes activated by infection and cellular stress that promote caspase-1 activation and subsequent inflammatory cytokine processing and cell death. It has been anticipated that inflammasome activity contributes to autoimmunity. However, we previously showed that macrophages from autoimmune New Zealand Black (NZB) mice lack NLRP3 inflammasome function, and their absent in melanoma 2 (AIM2) inflammasome responses are compromised by high expression of the AIM2 antagonist protein p202. Here we found that the point mutation leading to lack of NLRP3 expression occurred early in the NZB strain establishment, as it is shared with the related obese strain New Zealand Obese, but not with the unrelated New Zealand White (NZW) strain. The first cross progeny of NZB and NZW mice develop more severe lupus nephritis than the NZB strain. We have compared AIM2 and NLRP3 inflammasome function in macrophages from NZB, NZW, and NZB/W F1 mice. The NZW parental strain showed strong inflammasome function, whereas the NZB/W F1 have haploinsufficient expression of NLRP3 and show reduced NLRP3 and AIM2 inflammasome responses, particularly at low stimulus strength. It remains to be established whether the low inflammasome function could contribute to loss of tolerance and the onset of autoimmunity in NZB and NZB/W F1. However, with amplifying inflammatory stimuli through the course of disease, the NLRP3 response in the NZB/W F1 may be sufficient to contribute to kidney damage at later stages of disease.

Induction of IL-10 cytokine and the suppression of T cell proliferation by specific peptides from red cell band 3 and in vivo effects of these peptides on autoimmune hemolytic anemia in NZB mice

PurposeThe anion channel protein band 3 is the main target of the pathogenic red blood cells (RBC) autoantibodies in New Zealand black (NZB) mice. CD4 T cells from NZB mice with autoimmune hemolytic anemia respond to band 3. Previously, we have shown that IL-10 and peptides containing a dominant T cell epitope from red cell band 3 modulate autoimmune hemolytic anemia in NZB mice. Because of the immunoregulatory role of IL-10 in autoimmune diseases, we aim to identify individual band 3 peptides that induce high IL-10 production and simultaneously suppress CD4 T cell proliferation and to investigate the effect intranasal administration of IL-10 producing band 3 peptides on autoantibody responses of NZB mice.MethodsSplenic CD4 T cells of NZB mice were isolated and stimulated by co-culture of T cells with individual band 3 peptides. IL-10 production was measured by enzyme-linked immunosorbent assay and proliferative response of CD4 T cells was estimated by incorporation of [3H] thymidine assay. NZB mice were given either PBS, or peptides 25 (241–251) and 29 (282–296) or both peptides intranasally on three occasions at 2-day intervals. The mice were bled at 6, 10 and 18 weeks after peptide inhalation, and the number of RBC auto-antibodies was measured by DELAT and hematocrit values were assessed.ResultsPeptides 25 (241–251) and 29 (282–296) induced the highest IL-10 production by CD4 T cells. These peptides also inhibited the peak T cell proliferative response. 6 and 10 weeks after peptide inhalation, the total IgG, IgG1 and IgG2a in mice treated with both peptides 241–251 and 282–296 were significantly higher than control (P < 0.05). However, no significant difference in the mean hematocrit between of the peptide-treated mice and the control group was found.ConclusionsAlthough band 3 peptides 241–251 and 282–296 induced to the highest IL-10 production by CD4 T cells in vitro but fail to reverse the RBC autoantibody response in vivo. Modifications to improve solubility these peptides might help to modulate the immune response toward a T helper-2 profile and decrease the severity of anemia.

Disruption of Type I-IFN Signaling Decreases Autoimmune Development and Kidney Damage, But Not Anxiety-Like Behaviors in Lupus NZB Mice

Systemic lupus erythematosus (SLE) is a multisystem autoimmune disorder that is accompanied by neuropsychiatric manifestations such as anxiety. Despite undefined etio-pathogenesis for SLE, emerging evidence supports the importance of type I interferon (IFN) in the pathogenesis of autoimmune formation and renal damage both in SLE patients and lupus mice. Linkage mapping identified a quantitative trait locus (QTL) for elevated plus-maze (EPM) performance on the segment of chromosome 4 in lupus-prone New Zealand black (NZB) mice where the type I IFN-α genes are harbored. To determine possible roles of type I IFNs for anxiety-like behaviors in NZB mice, we evaluated the anxiety profile by EPM test in NZB mice with deficiency of type I-IFN receptor (IFNARKO). Consistent with previous observation, disruption of the type I-IFN signaling resulted in a dramatic attenuation in glomerulonephritis, splenomegaly and plasma anti-nuclear antibodies (ANA) in NZB mice. However, blockade of type I-IFN signaling had no effect on performance in the EPM by NZB/IFNARKO mice in comparison to wild type controls. The results support a pathogenic role for type I-IFN in autoimmune development and kidney inflammation. Nonetheless, type I-IFN signaling is not responsible for increased anxiety profile developed in these autoimmune mice.

Role of mir-15a/16-1 in early B cell development in a mouse model of chronic lymphocytic leukemia.

In both human chronic lymphocytic leukemia (CLL) and the New Zealand Black (NZB) murine model of CLL, decreased levels of microRNAs miR-15a/16 play an important role in the disease. Here we investigate the effects of this microRNA on early steps of B cell development and the capacity of miR-15a-deficient hematopoietic stem cells (HSC) and B1 progenitor cells (B1P) to reproduce CLL-like phenotype both in vitro and in vivo. Our results demonstrate that both miR-15a deficient HSC and B1P cells are capable of repopulating irradiated recipients and produce higher numbers of B1 cells than sources with normal miR-15a/16 levels. Furthermore, induced pluripotent stem (iPS) cells derived for the first time from NZB mice, provided insights into the B cell differentiation roadblock inherent in this strain. In addition, exogenously delivered miR-15a into the NZB derived B cell line provided valuable clues into novel targets such as Mmp10 and Mt2. Our data supports the hypothesis that miR-15a/16 deficient stem cells and B1Ps experience a maturation blockage, which contributes to B1 cells bias in development. This work will help understand the role of miR-15a in early events of CLL and points to B1P cells as potential cells of origin for this incurable disease.

The SOD1 transgene expressed in erythroid cells alleviates fatal phenotype in congenic NZB/NZW-F1 mice

Oxidative stress due to a superoxide dismutase 1 (SOD1) deficiency causes anemia and autoimmune responses, which are phenotypically similar to autoimmune hemolytic anemia (AIHA) and systemic lupus erythematosus (SLE) in C57BL/6 mice and aggravates AIHA pathogenesis in New Zealand black (NZB) mice. We report herein on an evaluation of the role of reactive oxygen species (ROS) in a model mouse with inherited SLE, that is, F1 mice of the NZB × New Zealand white (NZW) strain. The ROS levels within red blood cells (RBCs) of the F1 mice were similar to the NZW mice but lower compared to the NZB mice throughout adult period. Regarding SLE pathogenesis, we examined the effects of an SOD1 deficiency or the overexpression of human SOD1 in erythroid cells by establishing corresponding congenic F1 mice. A SOD1 deficiency caused an elevation in ROS production, methemoglobin content, and hyperoxidation of peroxiredoxin in RBC of the F1 mice, which were all consistent with elevated oxidative stress. However, while the overexpression of human SOD1 in erythroid cells extended the life span of the congenic F1 mice, the SOD1 deficiency had no effect on life span compared to wild-type F1 mice. It is generally recognized that NZW mice possess a larval defect in the immune system and that NZB mice trigger an autoimmune reaction in the F1 mice. Our results suggest that the oxidative insult originated from the NZB mouse background has a functional role in triggering an aberrant immune reaction, leading to fatal responses in F1 mice.

Synergistic Activity of Deguelin and Fludarabine in Cells from Chronic Lymphocytic Leukemia Patients and in the New Zealand Black Murine Model.

B-cell chronic lymphocytic leukemia (CLL) remains an incurable disease, and despite the improvement achieved by therapeutic regimes developed over the last years still a subset of patients face a rather poor prognosis and will eventually relapse and become refractory to therapy. The natural rotenoid deguelin has been shown to induce apoptosis in several cancer cells and cell lines, including primary human CLL cells, and to act as a chemopreventive agent in animal models of induced carcinogenesis. In this work, we show that deguelin induces apoptosis in vitro in primary human CLL cells and in CLL-like cells from the New Zealand Black (NZB) mouse strain. In both of them, deguelin dowregulates AKT, NFκB and several downstream antiapoptotic proteins (XIAP, cIAP, BCL2, BCL-XL and survivin), activating the mitochondrial pathway of apoptosis. Moreover, deguelin inhibits stromal cell-mediated c-Myc upregulation and resistance to fludarabine, increasing fludarabine induced DNA damage. We further show that deguelin has activity in vivo against NZB CLL-like cells in an experimental model of CLL in young NZB mice transplanted with spleen cells from aged NZB mice with lymphoproliferation. Moreover, the combination of deguelin and fludarabine in this model prolonged the survival of transplanted mice at doses of both compounds that were ineffective when administered individually. These results suggest deguelin could have potential for the treatment of human CLL.

Deficient NLRP3 and AIM2 Inflammasome Function in Autoimmune NZB Mice.

Inflammasomes are protein complexes that promote caspase activation, resulting in processing of IL-1β and cell death, in response to infection and cellular stresses. Inflammasomes have been anticipated to contribute to autoimmunity. The New Zealand Black (NZB) mouse develops anti-erythrocyte Abs and is a model of autoimmune hemolytic anemia. These mice also develop anti-nuclear Abs typical of lupus. In this article, we show that NZB macrophages have deficient inflammasome responses to a DNA virus and fungal infection. Absent in melanoma 2 (AIM2) inflammasome responses are compromised in NZB by high expression of the AIM 2 antagonist protein p202, and consequently NZB cells had low IL-1β output in response to both transfected DNA and mouse CMV infection. Surprisingly, we also found that a second inflammasome system, mediated by the NLR family, pyrin domain containing 3 (NLRP3) initiating protein, was completely lacking in NZB cells. This was due to a point mutation in an intron of the Nlrp3 gene in NZB mice, which generates a novel splice acceptor site. This leads to incorporation of a pseudoexon with a premature stop codon. The lack of full-length NLRP3 protein results in NZB being effectively null for Nlrp3, with no production of bioactive IL-1β in response to NLRP3 stimuli, including infection with Candida albicans. Thus, this autoimmune strain harbors two inflammasome deficiencies, mediated through quite distinct mechanisms. We hypothesize that the inflammasome deficiencies in NZB alter the interaction of the host with both microflora and pathogens, promoting prolonged production of cytokines that contribute to development of autoantibodies.

Oxidative stress as a potential causal factor for autoimmune hemolytic anemia and systemic lupus erythematosus.

The kidneys and the blood system mutually exert influence in maintaining homeostasis in the body. Because the kidneys control erythropoiesis by producing erythropoietin and by supporting hematopoiesis, anemia is associated with kidney diseases. Anemia is the most prevalent genetic disorder, and it is caused by a deficiency of glucose 6-phosphate dehydrogenase (G6PD), for which sulfhydryl oxidation due to an insufficient supply of NADPH is a likely direct cause. Elevated reactive oxygen species (ROS) result in the sulfhydryl oxidation and hence are another potential cause for anemia. ROS are elevated in red blood cells (RBCs) under superoxide dismutase (SOD1) deficiency in C57BL/6 mice. SOD1 deficient mice exhibit characteristics similar to autoimmune hemolytic anemia (AIHA) and systemic lupus erythematosus (SLE) at the gerontic stage. An examination of AIHA-prone New Zealand Black (NZB) mice, which have normal SOD1 and G6PD genes, indicated that ROS levels in RBCs are originally high and further elevated during aging. Transgenic overexpression of human SOD1 in erythroid cells effectively suppresses ROS elevation and ameliorates AIHA symptoms such as elevated anti-RBC antibodies and premature death in NZB mice. These results support the hypothesis that names oxidative stress as a risk factor for AIHA and other autoimmune diseases such as SLE. Herein we discuss the association between oxidative stress and SLE pathogenesis based mainly on the genetic and phenotypic characteristics of NZB and New Zealand white mice and provide insight into the mechanism of SLE pathogenesis.

Reactive oxygen species exacerbate autoimmune hemolytic anemia in New Zealand Black mice

Elevated reactive oxygen species (ROS) and oxidative damage occur in the red blood cells (RBCs) of SOD1-deficient C57BL/6 mice. This leads to autoimmune responses against RBCs in aged mice that are similar to autoimmune hemolytic anemia (AIHA). We examined whether a SOD1 deficiency and/or the human SOD1 transgene (hSOD1) would affect phenotypes of AIHA-prone New Zealand Black (NZB) mice by establishing three congenic strains: those lacking SOD1, those expressing hSOD1 under a GATA-1 promoter, and those lacking mouse SOD1 but expressing hSOD1. Levels of intracellular ROS and oxidative stress markers increased, and the severity of the AIHA phenotype was aggravated by a SOD1 deficiency. In contrast, the transgenic expression of hSOD1 in an erythroid cell-specific manner averted most of the AIHA phenotype evident in the SOD1-deficient mice and also ameliorated the AIHA phenotype in the mice possessing intrinsic SOD1. These data suggest that oxidative stress in RBCs may be an underlying mechanism for autoimmune responses in NZB mice. These results were consistent with the hypothetical role of reactive oxygen species in triggering the autoimmune reaction in RBCs and may provide a novel approach to mitigating the progression of AIHA by reducing oxidative stress.

Accelerated Development of Chronic Lymphocytic Leukemia in New Zealand Black Mice Expressing a Low Level of Interferon Regulatory Factor 4

A recent genome-wide SNP association study identified IRF4 as a major susceptibility gene for chronic lymphocytic leukemia (CLL). Moreover, the SNPs located in the 3' UTR of the IRF4 gene have been linked to a down-regulation of IRF4. However, whether a low level of IRF4 is critical for CLL development remains unclear. New Zealand Black (NZB) mice are a naturally occurring, late-onset mouse model of CLL. To examine the role of a reduced level of IRF4 in CLL development, we generated, through breeding, IRF4 heterozygous mutant mice in the NZB background (NZB IRF4(+/-)). Our results show that CLL development is accelerated dramatically in the NZB IRF4(+/-) mice. The average onset of CLL in NZB mice is 12 months, but CLL cells can be detected in NZB IRF4(+/-) mice at 3 months of age. By 5 months of age, 80% of NZB IRF4(+/-) mice developed CLL. CLL cells are derived from B1 cells in mice. Interestingly, NZB IRF4(+/-) B1 cells exhibit prolonged survival, accelerated self-renewal, and defects in differentiation. Although NZB IRF4(+/-) CLL cells are resistant to apoptosis, high levels of IRF4 inhibit their survival. High levels of IRF4 also reduce the survival of MEC-1 human CLL cells. Our analysis further reveals that high levels of IRF4 suppress Akt activity and can do so without the IRF4 DNA binding domain. Thus, our findings reveal a causal relationship between a low level of IRF4 and the development of CLL and establish IRF4 as a novel regulator in the pathogenesis of CLL.

Susceptibility loci for the defective foreign protein‐induced tolerance in New Zealand Black mice: Implication of epistatic effects of Fcgr2b and Slam family genes

In contrast to normal mice, autoimmune-prone New Zealand Black (NZB) mice are defective in susceptibility to tolerance induced by deaggregated bovine γ globulin (DBGG). To examine whether this defect is related to the loss of self-tolerance in autoimmunity, susceptibility loci for this defect were examined by genome-wide analysis using the F(2) intercross of nonautoimmune C57BL/6 (B6) and NZB mice. One NZB locus on the telomeric chromosome 1, designated Dit (Defective immune tolerance)-1, showed a highly significant linkage. This locus overlapped with a locus containing susceptibility genes for autoimmune disease, namely Fcgr2b and Slam family genes. To investigate the involvement of these genes in the defective tolerance to DBGG, we took advantage of two lines of Fcgr2b-deficient B6 congenic mice: one carries autoimmune-type, and the other carries B6-type, Slam family genes. Defective tolerance was observed only in Fcgr2b-deficient mice with autoimmune-type Slam family genes, indicating that epistatic effects of both genes are involved. Thus, common genetic mechanisms may underlie the defect in foreign protein antigen-induced tolerance and the loss of self-tolerance in NZB mouse-related autoimmune diseases.

Abrogation of pathogenic IgG autoantibody production in CD40L gene-deleted lupus-prone New Zealand Black mice

New Zealand Black (NZB) mice spontaneously develop a lupus-like autoimmune disease. Since CD40-CD40L interactions are important for B cell class-switch recombination and germinal center formation, we sought to understand the impact of these interactions on the immune abnormalities in NZB CD40L gene-deleted (CD40L(-/-)) mice in vivo. NZB.CD40L(-/-) mice demonstrated abrogation of all IgG autoantibodies tested and attenuated kidney disease. However, polyclonal B cell activation in vivo and B cell proliferation and class-switching in response to TLR ligands in vitro were preserved in the absence of CD40L in NZB mice. Although, plasmacytoid dendritic cell expansion and elevated BAFF production were unaffected by the absence of CD40L, there was some evidence that IFN-α-induced gene expression was reduced in the bone marrow of NZB.CD40L(-/-) mice. Our results suggest that CD40-CD40L interactions play an important role in promoting pathogenic IgG autoantibody production and kidney disease in NZB mice.

B Cell Activating Factor (BAFF) and T Cells Cooperate to Breach B Cell Tolerance in Lupus-Prone New Zealand Black (NZB) Mice

The presence of autoantibodies in New Zealand Black (NZB) mice suggests a B cell tolerance defect however the nature of this defect is unknown. To determine whether defects in B cell anergy contribute to the autoimmune phenotype in NZB mice, soluble hen egg lysozyme (sHEL) and anti-HEL Ig transgenes were bred onto the NZB background to generate double transgenic (dTg) mice. NZB dTg mice had elevated levels of anti-HEL antibodies, despite apparently normal B cell functional anergy in-vitro. NZB dTg B cells also demonstrated increased survival and abnormal entry into the follicular compartment following transfer into sHEL mice. Since this process is dependent on BAFF, BAFF serum and mRNA levels were assessed and were found to be significantly elevated in NZB dTg mice. Treatment of NZB sHEL recipient mice with TACI-Ig reduced NZB dTg B cell survival following adoptive transfer, confirming the role of BAFF in this process. Although NZB mice had modestly elevated BAFF, the enhanced NZB B cell survival response appeared to result from an altered response to BAFF. In contrast, T cell blockade had a minimal effect on B cell survival, but inhibited anti-HEL antibody production. The findings suggest that the modest BAFF elevations in NZB mice are sufficient to perturb B cell tolerance, particularly when acting in concert with B cell functional abnormalities and T cell help.

Abstract 4045: Restoring miR-15a/16 in the NZB mouse model of chronic lymphocytic leukemia reduces disease and enhances drug sensitivity

Abstract Alterations in the human 13q14 genomic region containing the microRNAS, mir-15a and mir-16-1 are present in a majority of human chronic lymphocytic leukemia (CLL). We have previously found the development of CLL in the New Zealand Black (NZB) murine model to be associated with a point mutation in the primary mir-15a/16-1 region, as well as a decrease in both mature miR-16 and miR-15a levels. Addition of exogenous miR-15a and miR-16 led to an accumulation of cells in G1 in both normal B cell and NZB-derived malignant B-1 cell lines. However, the NZB line had a significantly greater G1 accumulation, suggesting a restoration of cell cycle control upon exogenous miR-15a/16 addition. Our experiments demonstrated a reduction in protein levels of cyclin D1, a miR-15a/16 target and cell cycle regulator of G1/S transition, in the NZB cell line following miR-15a/16 addition. These miRNAs were shown to directly target the cyclin D1 3′UTR using a GFP lentiviral sensor. In vivo restoration of NZB with a miR-16-producing lentiviral vector resulted in the depletion of endogenous-transduced malignant aneuploid B-1 cells. In addition, experimentally increasing miR-16 in either a drug-resistant malignant NZB B-1 cell line or ex vivo splenic NZB B-1 cells augmented apoptosis induction by the following agents: genistein, a soy isoflavone tyrosine kinase inhibitor; nutlin, an MDM2 antagonist; and 2-fluoroadenine-9-B-D-arabinofuranoside, a purine nucleotide analog. Our data support a role for miR-16 in apoptosis induction, either alone, or in synergy with chemotherapeutic agents to increase their efficacy in murine CLL cells. This research was funded in part by the NJCCR pre-doctoral fellowship awarded to E.S. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 4045.

Implication of oxidative stress as a cause of autoimmune hemolytic anemia in NZB mice

We have recently shown that deficiency of the superoxide dismutase 1 gene (SOD1) causes anemia and autoimmune responses against red blood cells (RBCs) and that transgenic expression of human SOD1 in erythroid cells rescues them. Because these phenotypes observed in SOD1-deficient mice are similar to autoimmune hemolytic anemia (AIHA), a causal connection between reactive oxygen species (ROS) and AIHA was examined using an AIHA-prone New Zealand Black (NZB) mouse. ROS levels in RBCs were high in young NZB mice, compared to control New Zealand White (NZW) mice, and increased during aging. Methemoglobin and lipid peroxidation products were elevated during aging, consistent with the elevated oxidative stress in RBCs of NZB mice. Severity of anemia and levels of intracellular ROS were positively correlated. Levels of antibodies against 4-hydroxynonenal and acrolein were also elevated in NZB mice. Transgenic expression of human SOD1 protein in RBCs of NZB mice suppressed ROS in RBCs and decreased the death rate. When RBCs from C57BL/6 mice were injected weekly into the same strain of mice, production of anti-RBC antibody was observed only in mice that had been injected with oxidized RBCs. Thus, oxidation-mediated autoantibody production may be a more general mechanism for AIHA and related autoimmune diseases.

The New Zealand black mouse as a model for the development and progression of chronic lymphocytic leukemia

Similar to a subset of human patients who progress from monoclonal B lymphocytosis (MBL) to chronic lymphocytic leukemia (CLL), New Zealand Black (NZB) mice have an age-associated progression to CLL. The murine disease is linked to a genetic abnormality in microRNA mir-15a/16-1 locus, resulting in decreased mature miR-15a/16. Spleens of aging NZB were analyzed for the presence of B-1 cells via flow cytometry and for the presence of a side population (SP) via the ability of cells to exclude Hoechst 33342 dye. The SP was assayed for the presence of hyperdiploid B-1 clones and for the ability to differentiate into B-1 cells in vitro and transfer disease in vivo. In addition, enhanced apoptosis of chemoresistant NZB B-1 cells was examined by restoring miR-16 levels in nutlin-treated cells. Aging NZB mice develop a B-1 expansion and clonal development that evolves from MBL into CLL. An expansion in SP is also seen. Although the SP did contain increased cells with stem cell markers, they lacked malignant B-1 cells and did not transfer disease in vivo. Similar to B-1 cells, splenic NZB SP also has decreased miR-15a/16 when compared with C57Bl/6. Exogenous addition of miR-15a/16 to NZB B-1 cells resulted in increased sensitivity to nutlin. NZB serve as an excellent model for studying the development and progression of age-associated CLL. NZB SP cells do not seem to contain cancer stem cells, but rather the B-1 stem cell. NZB B-1 chemoresistance may be related to reduced miR-15a/16 expression.

The immature B‐cell subpopulation with low RAG1 expression is increased in the autoimmune New Zealand Black mouse

Receptor editing is believed to play a critical role in immunological tolerance by altering the specificity of autoreactive B cells that emerge in the bone marrow. To study whether receptor editing is altered in autoimmune disease, recombination activation gene 1 (rag1) transcription in B cells from New Zealand Black (NZB) mice was examined by introducing a GFP gene at the rag1 locus. Female NZB(RAG1-GFP) mice generated autoantibodies and glomerular immune complexes. NZB(RAG1-GFP) mice did not display increased RAG1-GFP signal in B-1 and B-2 cells from the spleen and peritoneal cavity even following in vitro stimulation compared with C57BL/6(RAG1-GFP) control mice. The early B cells in the bone marrow were classified into RAG1-GFP(-) and RAG1-GFP(+) subpopulations. The RAG1-GFP(-) immature B-cell population was in the minority in C57BL/6(RAG1-GFP) mice but was markedly increased in NZB(RAG1-GFP) mice. RAG1-GFP(-) immature B cells from NZB(RAG1-GFP) mice differentiated into anti-dsDNA Ab-producing cells after stimulation by LPS in vitro. RAG1-GFP(-) immature B cells from NZB(RAG1-GFP) mice displayed a different expression profile of transcription factors required for receptor editing, including pax5 and irf4, in comparison with the RAG1-GFP(+) immature B-cell population. In conclusion, the early B-cell subpopulation, which exhibits low RAG1 expression and presumably concomitantly low receptor editing, was found to be increased in NZB mice.

Macrophage Impairment Underlies Airway Occlusion in Primary Respiratory Syncytial Virus Bronchiolitis

Although respiratory syncytial virus (RSV) infection is the most important cause of bronchiolitis in infants, the pathogenesis of RSV disease is poorly described. We studied histopathologic changes in a panel of lung tissue specimens obtained from infants with fatal cases of primary RSV infection. In these tissues, airway occlusion with accumulations of infected, apoptotic cellular debris and serum protein was consistently observed. Similar observations were found after RSV infection in New Zealand black (NZB) mice, which have constitutive deficiencies in macrophage function, but not in BALB/c mice. A deficiency in the number of alveolar macrophages in NZB mice appears to be central to enhanced disease, because depletion of alveolar macrophages in BALB/c mice before RSV exposure resulted in airway occlusion. In mice with insufficient numbers of macrophages, RSV infection yielded an increased viral load and enhanced expression of type I interferon-associated genes at the height of disease. Together, our data suggest that innate, rather than adaptive, immune responses are critical determinants of the severity of RSV bronchiolitis.

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

Regulatory T cells (Tregs) play an important role in protection against autoimmune disease and are also known to be potent inhibitors of anti-tumor immune responses. The New Zealand Black (NZB) mouse is a murine model for both autoimmune diseases, since high levels of autoantibodies are present, and human CLL, due to the expansion of malignant B-1 cells. In this study, we examined the functional role of CD4 +CD25 + Foxp3 + Tregs in these different manifestations. Flow cytometric analysis showed increased levels of Tregs in NZB mice compared to healthy C57Bl/6 controls. Aged NZB mice that have developed a B-1 cell malignancy identified as IgM +CD5 +, have the most pronounced increase in Tregs. Ex vivo treatment of splenocytes from NZB mice with IFN-α resulted in a decrease in the frequency of Tregs and malignant B-1 cells. In vivo treatment of both NZB and C57Bl/6 mice with poly (I:C), a potent inducer of IFN-α, also led to a decrease in the levels of Tregs and malignant B-1 cells (NZB only) while amplifying autoimmune manifestations. These results indicate that while high levels of Tregs found in NZB mice might suppress a more severe autoimmune disease, they may also contribute to the development of the B cell malignancy.