Maackia amurensis seed lectin (MASL) ameliorates articular cartilage destruction and increases movement velocity of mice with TNFα induced rheumatoid arthritis.

Up to 70 million people around the world suffer from rheumatoid arthritis. Current treatment options have varied efficacy and can cause unwanted side effects. New approaches are needed to treat this condition. Sialic acid modifications on chondrocyte receptors have been associated with arthritic inflammation and joint destruction. For example, the transmembrane mucin receptor protein podoplanin (PDPN) has been identified as a functionally relevant receptor that presents extracellular sialic acid motifs. PDPN signaling promotes inflammation and invasion associated with arthritis and, therefore, has emerged as a target that can be used to inhibit arthritic inflammation. Maackia amurensis seed lectin (MASL) can target PDPN on chondrocytes to decrease inflammatory signaling cascades and reduce cartilage destruction in a lipopolysaccharide induced osteoarthritis mouse model. Here, we investigated the effects of MASL on rheumatoid arthritis progression in a TNFα transgenic (TNF-Tg) mouse model. Results from this study indicate that MASL can be administered orally to ameliorate joint malformation and increase velocity of movement exhibited by these TNF-Tg mice. These data support the consideration of MASL as a potential treatment for rheumatoid arthritis.

American Association of Immunologists Recommendations for an Undergraduate Course in Immunology.

Identifying the "essential" components of an undergraduate immunology lecture course can be daunting because of the varying postgraduate pathways students take. The American Association of Immunologists Education Committee commissioned an Ad Hoc Committee, representing undergraduate, graduate, and medical institutions as well as the biotechnology community, to develop core curricular recommendations for teaching immunology to undergraduates. In a reiterative process involving the American Association of Immunologists teaching community, 14 key topics were identified and expanded to include foundational concepts, subtopics and examples, and advanced subtopics, providing a flexible list for curriculum development and avenues for higher-level learning. Recommendations for inclusive and antiracist teaching that outline opportunities to meet the needs of diverse student populations were also developed. The consensus recommendations can be used to accommodate various course settings and will bridge undergraduate and graduate teaching and prepare diverse students for subsequent careers in the biomedical field.

Differential cellular composition of human palatine and pharyngeal tonsils.

OBJECTIVE: The goal of this study was to gain a better understanding of the potential functional specialization of palatine and pharyngeal tonsils, by comparing their cellular composition in paired specimens from a large cohort of adenotonsillectomy patients. DESIGN: Resident B cell, T cell, dendritic cell, and stromal cell subsets were characterized using multicolor flow cytometry in palatine and pharyngeal tonsil specimens from 27 patients, age 2-34 years. RESULTS: Paired comparisons showed highly significant intra-individual differences in resident cell subsets of palatine and pharyngeal tonsils. Palatine tonsils harbored higher fractions of germinal center B cells/plasmablasts and IgD- CD27- double-negative B cells, and conversely lower fractions of IgD + CD38- resting naïve B cells compared to pharyngeal tonsils. Palatine tonsils also showed lower fractions of plasmacytoid dendritic cells, and higher percentages of two subsets of stromal cells - fibroblastic reticular cells and lymphatic endothelial cells - compared to pharyngeal tonsils from the same individual. CONCLUSIONS: Despite their physical proximity and histological similarities, palatine and pharyngeal tonsils display marked intra-individual differences in their cellular composition with regard to functionally important immune and stromal subsets. These differences are likely to have immunologic, pathologic, and physiologic significance.

Animal models of rheumatoid pain: experimental systems and insights.

Severe chronic pain is one of the hallmarks and most debilitating manifestations of inflammatory arthritis. It represents a significant problem in the clinical management of patients with common chronic inflammatory joint conditions such as rheumatoid arthritis, psoriatic arthritis and spondyloarthropathies. The functional links between peripheral inflammatory signals and the establishment of the neuroadaptive mechanisms acting in nociceptors and in the central nervous system in the establishment of chronic and neuropathic pain are still poorly understood, representing an area of intense study and translational priority. Several well-established inducible and spontaneous animal models are available to study the onset, progression and chronicization of inflammatory joint disease, and have been instrumental in elucidating its immunopathogenesis. However, quantitative assessment of pain in animal models is technically and conceptually challenging, and it is only in recent years that inflammatory arthritis models have begun to be utilized systematically in experimental pain studies using behavioral and neurophysiological approaches to characterize acute and chronic pain stages. This article aims primarily to provide clinical and experimental rheumatologists with an overview of current animal models of arthritis pain, and to summarize emerging findings, challenges and unanswered questions in the field.

Chronic exposure to tumor necrosis factor in vivo induces hyperalgesia, upregulates sodium channel gene expression and alters the cellular electrophysiology of dorsal root ganglion neurons.

The goal of these studies was to investigate the links between chronic exposure to the pro-inflammatory cytokine tumor necrosis factor (TNF), hyperalgesia and the excitability of dorsal root ganglion (DRG) sensory neurons. We employed transgenic mice that constitutively express TNF (TNFtg mice), a well-established model of chronic systemic inflammation. At 6 months of age, TNFtg mice demonstrated increased sensitivity to both mechanical and thermal heat stimulation relative to aged-matched wild-type controls. These increases in stimulus-evoked behaviors are consistent with nociceptor sensitization to normal physiological stimulation. The mechanisms underlying nociceptor sensitization were investigated using single-cell analysis to quantitatively compare gene expression in small-diameter (<30µm) DRG neurons. This analysis revealed the upregulation of mRNA encoding for tetrodotoxin-resistant (TTX-R) sodium (Na+) channels (Nav1.8, Nav1.9), Na+ channel ß subunits (ß1-ß3), TNF receptor 1 (TNFR1) and p38α mitogen-activated protein kinase in neurons of TNFtg mice. Whole-cell electrophysiology demonstrated a corresponding increase in TTX-R Na+ current density, hyperpolarizing shifts in activation and steady-state inactivation, and slower recovery from inactivation in the TNFtg neurons. Increased overlap of activation and inactivation in the TNFtg neurons produces inward Na+ currents at voltages near the resting membrane potential of sensory neurons (i.e. window currents). The combination of increased Na+ current amplitude, hyperpolarized shifts in Na+ channel activation and increased window current predicts a reduction in the action potential threshold and increased firing of small-diameter DRG neurons. Together, these data suggest that increases in the expression of Nav1.8 channels, regulatory ß1 subunits and TNFR1 contribute to increased nociceptor excitability and hyperalgesia in the TNFtg mice.

Brief Report: Treatment of Tumor Necrosis Factor-Transgenic Mice With Anti-Tumor Necrosis Factor Restores Lymphatic Contractions, Repairs Lymphatic Vessels, and May Increase Monocyte/Macrophage Egress.

OBJECTIVE: Recent studies have demonstrated that there is an inverse relationship between lymphatic egress and inflammatory arthritis in affected joints. As a model, tumor necrosis factor (TNF)-transgenic mice develop advanced arthritis following draining lymph node (LN) collapse, and loss of lymphatic contractions downstream of inflamed joints. It is unknown if these lymphatic deficits are reversible. This study was undertaken to test the hypothesis that anti-TNF therapy reduces advanced erosive inflammatory arthritis, associated with restoration of lymphatic contractions, repair of damaged lymphatic vessels, and evidence of increased monocyte egress. METHODS: TNF-transgenic mice with advanced arthritis and collapsed popliteal LNs were treated with anti-TNF monoclonal antibody (10 mg/kg weekly) or placebo for 6 weeks, and effects on knee synovitis, lymphatic vessel ultrastructure and function, and popliteal LN cellularity were assessed by ultrasound, histology, transmission electron microscopy (TEM), near-infrared indocyanine green imaging, and flow cytometry. RESULTS: Anti-TNF therapy significantly decreased synovitis (∼5-fold; P < 0.05 versus placebo), restored lymphatic contractions, and significantly increased the number of popliteal LN monocyte/macrophages (∼2-fold; P < 0.05 versus placebo). TEM demonstrated large activated macrophages attached to damaged lymphatic endothelium in mice with early arthritis, extensively damaged lymphatic vessels in placebo-treated mice with advanced arthritis, and rolling leukocytes in repaired lymphatic vessels in mice responsive to anti-TNF therapy. CONCLUSION: These findings support the concept that anti-TNF therapy ameliorates erosive inflammatory arthritis, in part via restoration of lymphatic vessel contractions and potential enhancement of inflammatory cell egress.

Increased numbers of CD23(+) CD21(hi) Bin-like B cells in human reactive and rheumatoid arthritis lymph nodes.

A unique population of CD23(+) CD21(high) B cells in inflamed nodes (Bin) has been shown to accumulate in lymph nodes (LNs) draining inflamed joints of TNF-transgenic (TNF-tg) mice. Bin cells contribute to arthritis flare in mice by distorting node architecture and hampering lymphatic flow, but their existence in human inflamed LNs has not yet been described. Here, we report the characterization of resident B-cell populations in fresh popliteal lymph nodes (PLNs) from patients with severe lower limb diseases (non-RA) and rheumatoid arthritis (RA) patients, and from banked, cryopreserved reactive and normal human LN single cell suspension samples. Bin-like B cells were shown to be significantly increased in reactive LNs, and strikingly elevated (>30% of total) in RA samples. Histopathology and immunofluorescence analyses were consistent with B follicular hyperplasia and histological alterations in RA vs. non-RA PLNs. This is the first description of Bin-like B cells in human inflamed LNs. Consistent with published mouse data, this population appears to be associated with inflammatory arthritis and distortion of LN architecture. Further analyses are necessary to assess the role of CD23(+) CD21(hi) Bin-like B cells in RA pathogenesis and arthritic flare.

Baseline CXCL10 and CXCL13 levels are predictive biomarkers for tumor necrosis factor inhibitor therapy in patients with moderate to severe rheumatoid arthritis: a pilot, prospective study.

BACKGROUND: TNF inhibitors have been used as a treatment for moderate to severe RA patients. However, reliable biomarkers that predict therapeutic response to TNF inhibitors are lacking. In this study, we investigated whether chemokines may represent useful biomarkers to predict the response to TNF inhibitor therapy in RA. METHODS: RA patients (n = 29) who were initiating adalimumab or etanercept were recruited from the rheumatology clinics at Cooper University Hospital. RA patients were evaluated at baseline and 14 weeks after TNF inhibitor therapy, and serum levels of CXCL10, CXCL13, and CCL20 were measured by ELISA. Responders (n = 16) were defined as patients who had good or moderate response at week 14 by EULAR response criteria, and nonresponders (n = 13) were defined as having no response. RESULTS: Responders had higher levels of baseline CXCL10 and CXCL13 compared to nonresponders (p = 0.03 and 0.002 respectively). There was no difference in CCL20 levels. CXCL10 and CXCL13 were highly correlated with each other, and were higher in seropositive RA patients. CXCL10 and CXCL13 levels were decreased after TNF inhibitor therapy in responders. Baseline additive levels of CXCL10 + 13 were correlated with changes in DAS score at 14 weeks after TNF inhibitor therapy (r = 0.42, p = 0.03), and ROC curve analyses for predictive ability of CXCL10 + 13 showed an AUC of 0.83. CONCLUSIONS: Elevated baseline levels of CXCL10 and CXCL13 were associated with favorable response to TNF inhibitor therapy in RA. Subjects with high CXCL10 and high CXCL13 may represent a subset of RA patients whose inflammatory reactions are primarily driven by TNF.

The CD27-CD70 pathway and pathogenesis of autoimmune disease.

OBJECTIVE: To critically examine current evidence regarding the role of the CD27-CD70 pathway in the pathophysiology of autoimmune disease with a focus on understanding the contributions of this pathway as a potential new therapeutic target for systemic lupus erythematosus and rheumatoid arthritis. METHODS: A PubMed search for articles was conducted using the following key words: ("CD27" OR "CD70") AND ("autoimmune disease" OR "systemic lupus erythematosus" OR "rheumatoid arthritis"). The search was limited to publications in English and included human and animal studies. The reference lists of identified articles were searched for further relevant citations. Publications on the list that was developed by this approach were assessed and those with relevance to CD27-CD70 pathway mediated pathophysiology in autoimmune disease were chosen for the detailed review. RESULTS: Data from human diseases and animal models document a major role for the CD27-CD70 receptor-ligand pair in providing signals that regulate T and B lymphocyte activation. The membrane receptor CD27 and its soluble form (sCD27) transmit co-stimulatory signals and induce activation and proliferation of T and B lymphocytes. CD70-expressing CD4 T lymphocytes are increased in autoimmune disease including systemic lupus erythematosus and rheumatoid arthritis and have been shown to produce pro-inflammatory cytokines. At the same time, preclinical evidence suggests that the outcome of CD27-CD70 signals may vary qualitatively between cell subsets and differentiation stages, especially for B lymphocytes. Blockade of the CD27-CD70 pathway has been shown to ameliorate disease manifestations in animal models including murine collagen-induced arthritis and experimental colitis. CONCLUSION: Current evidence from animal models and human diseases suggests that CD27-CD70 pathway contributes to the pathophysiology of autoimmunity. Although a number of basic questions still remain open, the available findings suggest that targeting the components of this pathway could provide useful and novel therapeutic interventions.

TNF signals are dispensable for the generation of CD23+ CD21/35-high CD1d-high B cells in inflamed lymph nodes.

Tumor necrosis factor (TNF) is a key cytokine in rheumatoid arthritis (RA) pathogenesis, as underscored by the clinical effectiveness of TNF antagonists. While several of TNF's key targets in RA are well understood, its many pleiotropic effects remain to be elucidated. TNF-transgenic mice develop inflammatory-erosive arthritis associated with disruption of draining lymph node histology and function, and accumulation of B cells with unique phenotypic and functional features consistent with contribution to pathogenesis (B cells in inflamed nodes, Bin). Bin cell induction depends on the inflamed microenvironment, but the specific signals are unknown. Using anti-TNF treatment and TNF-receptor-deficient mice, here we show that Bin cells are induced and maintained independently of B cell-intrinsic TNF signals.

Efficacy of B cell depletion therapy for murine joint arthritis flare is associated with increased lymphatic flow.

OBJECTIVE: B cell depletion therapy ameliorates rheumatoid arthritis by mechanisms that are incompletely understood. Arthritis flare in tumor necrosis factor (TNF)-transgenic mice is associated with efferent lymph node (LN) "collapse," triggered by B cell translocation into lymphatic spaces and decreased lymphatic drainage. The aim of this study was to examine whether the efficacy of B cell depletion therapy is associated with restoration of lymphatic drainage due to removal of obstructing nodal B cells. METHODS: We used contrast-enhanced magnetic resonance imaging, indocyanine green near-infrared imaging, and intravital immunofluorescence imaging to longitudinally assess synovitis, lymphatic flow, and cell migration in lymphatic vessels in TNF-transgenic mice. We conducted tests to determine whether the efficacy of B cell depletion therapy is associated with restoration of lymphatic draining and cell egress from arthritic joints. RESULTS: Unlike active lymphatics to normal and prearthritic knees, afferent lymphatic vessels to collapsed LNs in inflamed knees do not pulse. Intravital immunofluorescence imaging demonstrated that CD11b+ monocyte/macrophages in lymphatic vessels afferent to expanding LNs travel at high velocity (mean±SD 186±37 µm/second), while these cells are stationary in lymphatic vessels afferent to collapsed popliteal LNs. B cell depletion therapy for arthritis flares in TNF-transgenic mice significantly decreased knee synovium volume (by 50% from the baseline level) and significantly increased lymphatic clearance compared with placebo (P<0.05). This increased lymphatic drainage restored macrophage egress from inflamed joints without recovery of the lymphatic pulse. CONCLUSION: These results support a novel mechanism in which B cell depletion therapy for joint arthritis flares lessens inflammation by increasing lymphatic drainage and subsequent migration of cells and cytokines from the synovial space.

Peroxisome proliferator-activated receptor γ B cell-specific-deficient mice have an impaired antibody response.

Peroxisome proliferator-activated receptors (PPARs) are members of the nuclear hormone receptor superfamily. PPARγ, a ligand-activated transcription factor, has important anti-inflammatory and antiproliferative functions, and it has been associated with diseases including diabetes, scarring, and atherosclerosis, among others. PPARγ is expressed in most bone marrow-derived cells and influences their function. PPARγ ligands can stimulate human B cell differentiation and promote Ab production. A knowledge gap is that the role of PPARγ in B cells under physiological conditions is not known. We developed a new B cell-specific PPARγ (B-PPARγ) knockout mouse and explored the role of PPARγ during both the primary and secondary immune response. In this article, we show that PPARγ deficiency in B cells decreases germinal center B cells and plasma cell development, as well as the levels of circulating Ag-specific Abs during a primary challenge. Inability to generate germinal center B cells and plasma cells is correlated to decreased MHC class II expression and decreased Bcl-6 and Blimp-1 levels. Furthermore, B-PPARγ-deficient mice have an impaired memory response, characterized by low titers of Ag-specific Abs and low numbers of Ag-experienced, Ab-secreting cells. However, B-PPARγ-deficient mice have no differences in B cell population distribution within primary or secondary lymphoid organs during development. This is the first report, to our knowledge, to show that, under physiological conditions, PPARγ expression in B cells is required for an efficient B cell-mediated immune response as it regulates B cell differentiation and Ab production.

CD23+ CD21(high) CD1d(high) B cells in inflamed lymph nodes are a locally differentiated population with increased antigen capture and activation potential.

CD23(+)CD21(high)CD1d(high) B cells in inflamed nodes (Bin cells) accumulate in the lymph nodes (LNs) draining inflamed joints of the TNF-α-transgenic mouse model of rheumatoid arthritis and are primarily involved in the significant histological and functional LN alterations that accompany disease exacerbation in this strain. In this study, we investigate the origin and function of Bin cells. We show that adoptively transferred GFP(+) sorted mature follicular B (FoB) cells home preferentially to inflamed LNs of TNF-α-transgenic mice where they rapidly differentiate into Bin cells, with a close correlation with the endogenous Bin fraction. Bin cells are also induced in wild-type LNs after immunization with T-dependent Ags and display a germinal center phenotype at higher rates compared with FoB cells. Furthermore, we show that Bin cells can capture and process Ag-immune complexes in a CD21-dependent manner more efficiently than can FoB cells, and they express greater levels of MHC class II and costimulatory Ags CD80 and CD86. We propose that Bin cells are a previously unrecognized inflammation-induced B cell population with increased Ag capture and activation potential, which may facilitate normal immune responses but may contribute to autoimmunity when chronic inflammation causes their accumulation and persistence in affected LNs.

CD23(+)/CD21(hi) B-cell translocation and ipsilateral lymph node collapse is associated with asymmetric arthritic flare in TNF-Tg mice.

INTRODUCTION: Rheumatoid arthritis (RA) is a chronic autoimmune disease with episodic flares in affected joints. However, how arthritic flare occurs only in select joints during a systemic autoimmune disease remains an enigma. To better understand these observations, we developed longitudinal imaging outcomes of synovitis and lymphatic flow in mouse models of RA, and identified that asymmetric knee flare is associated with ipsilateral popliteal lymph node (PLN) collapse and the translocation of CD23(+)/CD21(hi) B-cells (B-in) into the paracortical sinus space of the node. In order to understand the relationship between this B-in translocation and lymph drainage from flaring joints, we tested the hypothesis that asymmetric tumor necrosis factor (TNF)-induced knee arthritis is associated with ipsilateral PLN and iliac lymph node (ILN) collapse, B-in translocation, and decreased afferent lymphatic flow. METHODS: TNF transgenic (Tg) mice with asymmetric knee arthritis were identified by contrast-enhanced (CE) magnetic resonance imaging (MRI), and PLN were phenotyped as "expanding" or "collapsed" using LNcap threshold = 30 (Arbitrary Unit (AU)). Inflammatory-erosive arthritis was confirmed by histology. Afferent lymphatic flow to PLN and ILN was quantified by near infrared imaging of injected indocyanine green (NIR-ICG). The B-in population in PLN and ILN was assessed by immunohistochemistry (IHC) and flow cytometry. Linear regression analyses of ipsilateral knee synovial volume and afferent lymphatic flow to PLN and ILN were performed. RESULTS: Afferent lymph flow to collapsed nodes was significantly lower (P < 0.05) than flow to expanding nodes by NIR-ICG imaging, and this occurred ipsilaterally. While both collapsed and expanding PLN and ILN had a significant increase (P < 0.05) of B-in compared to wild type (WT) and pre-arthritic TNF-Tg nodes, B-in of expanding lymph nodes (LN) resided in follicular areas while B-in of collapsed LN were present within LYVE-1+ lymphatic vessels. A significant correlation (P < 0.002) was noted in afferent lymphatic flow between ipsilateral PLN and ILN during knee synovitis. CONCLUSIONS: Asymmetric knee arthritis in TNF-Tg mice occurs simultaneously with ipsilateral PLN and ILN collapse. This is likely due to translocation of the expanded B-in population to the lumen of the lymphatic vessels, resulting in a dramatic decrease in afferent lymphatic flow. PLN collapse phenotype can serve as a new biomarker of knee flare.

Long-term immunologically competent human peripheral lymphoid tissue cultures in a 3D bioreactor.

Peripheral lymphoid organs (PLOs), the primary sites of development of adaptive immune responses, display a complex structural organization reflecting separation of cellular subsets (e.g., T and B lymphocytes) and functional compartments which is critical for immune function. The generation of in vitro culture systems capable of recapitulating salient features of PLOs for experimental, biotechnological, and clinical applications would be highly desirable, but has been hampered so far by the complexity of these systems. We have previously developed a three-dimensional bioreactor system for long-term, functional culture of human bone marrow cells on macroporous microspheres in a packed-bed bioreactor with frequent medium change. Here we adapt the same system for culture of human primary cells from PLOs (tonsil) in the absence of specific exogenous growth factors or activators. Cells in this system displayed higher viability over several weeks, and maintain population diversity and cell surface markers largely comparable to primary cells. Light microscopy showed cells organizing in large diverse clusters within the scaffold pores and presence of B cell-enriched areas. Strikingly, these cultures generated a significant number of antibody-producing B cells when challenged with a panel of diverse antigens, as expected from a lymphoid tissue. Thus the three-dimensional tonsil bioreactor culture system may serve as a useful model of PLOs by recapitulating their structural organization and function ex vivo.

Expanded CD23(+)/CD21(hi) B cells in inflamed lymph nodes are associated with the onset of inflammatory-erosive arthritis in TNF-transgenic mice and are targets of anti-CD20 therapy.

Anti-CD20 B cell depletion therapy (BCDT) is very effective for some patients with rheumatoid arthritis (RA); however the pathogenic role of B lymphocytes in RA and the primary targets of BCDT are unknown. The human TNF transgenic (hTNF-Tg) mouse model of RA displays a chronic, progressive disease that spreads from distal to proximal joints and is generally considered to be adaptive immune system independent. We have previously reported that knee arthritis in hTNF-Tg mice is accompanied by structural and functional changes of the adjoining popliteal lymph node (PLN), detectable by contrast-enhanced magnetic resonance imaging. To better understand these changes, in this paper we show that onset of knee synovitis and focal erosions are paralleled by PLN contraction and accumulation of large numbers of B cells in the lymphatic sinus spaces within the node. Flow cytometry from TNF-Tg mice 2, 4-5, and 8-12 mo old demonstrated that B cell accumulation in the PLN follows ankle arthritis, but commences before knee disease, and involves early expansion of CD21(hi), CD23(+), IgM(hi), CD1d(+), activation marker-negative, polyclonal B cells that are found to be specifically restricted to lymph nodes draining inflamed, arthritic joints. The same B cell population also accumulates in PLNs of K/BxN mice with autoantigen-dependent arthritis. Strikingly, we show that BCDT ameliorates hTNF-Tg disease and clears follicular and CD21(hi), CD23(+) B cells from the PLNs. On the basis of these findings, we propose a model whereby B cells contribute to arthritis in mice, and possibly RA, by directly affecting the structure, composition, and function of joint-draining lymph nodes.

Susceptibility to autoimmunity and B cell resistance to apoptosis in mice lacking androgen receptor in B cells.

Estrogens have been linked to a higher female incidence of autoimmune diseases. The role of androgen and the androgen receptor (AR) in autoimmune diseases, however, remains unclear. Here we report that the lack of AR in B cells in different strains of mice, namely general AR knockout, B cell-specific AR knockout, and naturally occurring testicular feminization mutation AR-mutant mice, as well as castrated wild-type mice, results in increased B cells in blood and bone marrow. Analysis of the targeted mice, together with bone marrow transplantation using Rag1(-/-) recipients, overexpression of retrovirally encoded AR-cDNA, and small interfering RNA-mediated AR mRNA knockdown approaches also show that the B cell expansion results from resistance to apoptosis and increased proliferation of bone marrow precursor B cells, accompanied by changes in several key modulators related to apoptosis, such as Fas/FasL signals, caspases-3/-8, nuclear factor-kappaB, and Bcl-2. We also show that the effects of AR loss are, in part, B cell intrinsic. Mice bearing AR-deficient B cells show increased levels of serum IgG2a and IgG3 as well as basal double-stranded DNA-IgG antibodies and are more vulnerable to development of collagen-induced arthritis. Together, these data indicate that androgen/AR play a crucial role in B cell homeostasis and tolerance. Therapies targeting AR might provide an alternative strategy with which to battle autoimmune diseases.

The biologic properties of leukemias arising from BCR/ABL-mediated transformation vary as a function of developmental origin and activity of the p19ARF gene.

Recent reports have shown that upon expression of appropriate oncogenes, both stem cells and more differentiated progenitor populations can serve as leukemia-initiating cells. These studies suggest that oncogenic mutations subvert normal development and induce reacquisition of stem-like features. However, no study has described how specific mutations influence the ability of differentiating cell subsets to serve as leukemia-initiating cells and if varying such cellular origins confers a functional difference. We have examined the role of the tumor suppressor gene p19(ARF) in a murine model of acute lymphoblastic leukemia and found that loss of p19(ARF) changes the spectrum of cells capable of tumor initiation. With intact p19(ARF), only hematopoietic stem cells (HSCs) can be directly transformed by BCR/ABL expression. In a p19(ARF)-null genetic background expression of the BCR/ABL fusion protein renders functionally defined HSCs, common lymphoid progenitors (CLP), and precursor B-lymphocytes competent to generate leukemia stem cells. Furthermore, we show that leukemias arising from p19(ARF)-null HSC versus pro-B cells differ biologically, including relative response to drug insult. Our observations elucidate a unique mechanism by which heterogeneity arises in tumor populations harboring identical genetic lesions and show that activity of p19(ARF) profoundly influences the nature of tumor-initiating cells during BCR/ABL-mediated leukemogenesis.