Hermansky Pudlak type 2 syndrome (HPS2) is a rare autosomal recessive primary immune deficiency caused by mutations on β3A gene (AP3B1 gene). The defect results in the impairment of the adaptor protein 3 (AP-3) complex, responsible for protein sorting to secretory lysosomes leading to oculo-cutaneous albinism, bleeding disorders and immunodeficiency. We have studied peripheral blood and lymph node biopsies from two siblings affected by HPS2. Lymph node histology showed a nodular lymphocyte predominance type Hodgkin lymphoma (NLPHL) in both HPS2 siblings. By immunohistochemistry, CD8 T-cells from HPS2 NLPHL contained an increased amount of perforin (Prf) + suggesting a defect in the release of this granules-associated protein. By analyzing peripheral blood immune cells we found a significant reduction of circulating NKT cells and of CD56brightCD16− Natural Killer (NK) cells subset. Functionally, NK cells were defective in their cytotoxic activity against tumor cell lines including Hodgkin Lymphoma as well as in IFN-γ production. This defect was associated with increased baseline level of CD107a and CD63 at the surface level of unstimulated and IL-2-activated NK cells. In summary, these results suggest that a combined and profound defect of innate and adaptive effector cells might explain the susceptibility to infections and lymphoma in these HPS2 patients.
In contrast to the commonly indolent clinical behavior of nodular lymphocyte predominant Hodgkin lymphoma (NLPHL), T cell/histiocyte rich large B cell lymphoma (THRLBCL) is frequently diagnosed in advanced clinical stages and has a poor prognosis. Besides the different clinical presentations of these lymphoma entities, there are variants of NLPHL with considerable histopathologic overlap compared to THRLBCL. Especially THRLBCL-like NLPHL, a diffuse form of NLPHL, often presents a histopathologic pattern similar to THRLBCL, suggesting a close relationship between both lymphoma entities. To corroborate this hypothesis, we performed gene expression profiling of microdissected tumor cells of NLPHL, THRLBCL-like NLPHL and THRLBCL. In unsupervised analyses, the lymphomas did not cluster according to their entity. Moreover, even in supervised analyses, very few consistently differentially expressed transcripts were found, and for these genes the extent of differential expression was only moderate. Hence, there are no clear and consistent differences in the gene expression of the tumor cells of NLPHL, THRLBCL-like NLPHL and THRLBCL. Based on the gene expression studies, we identified BAT3/BAG6, HIGD1A, and FAT10/UBD as immunohistochemical markers expressed in the tumor cells of all three lymphomas. Characterization of the tumor microenvironment for infiltrating T cells and histiocytes revealed significant differences in the cellular composition between typical NLPHL and THRLBCL cases. However, THRLBCL-like NLPHL presented a histopathologic pattern more related to THRLBCL than NLPHL. In conclusion, NLPHL and THRLBCL may represent a spectrum of the same disease. The different clinical behavior of these lymphomas may be strongly influenced by differences in the lymphoma microenvironment, possibly related to the immune status of the patient at the timepoint of diagnosis.
Natural killer (NK) cells are classically viewed as lymphocytes that provide innate surveillance against virally-infected cells and tumor cells through release of cytolytic mediators and IFN-γ. In humans, blood CD56dim NK cells specialize in lysis of cell targets1. In lymph nodes, CD56bright NK cells secrete IFN-γ cooperating with dendritic cells (DC) and T cells in the generation of adaptive responses1, 2. Here we report the characterization of a human NK cell subset located in mucosa-associated lymphoid tissues (MALT), such as tonsils and Payer’s patches, which is hard-wired to secrete interleukin (IL)-22, IL-26, and leukaemia inhibitory factor (LIF). These NK cells, which we refer to as NK-22 cells, are triggered by acute exposure to IL-23. In vitro, NK-22-secreted cytokines stimulate epithelial cells to secrete IL-10, proliferate and express a variety of mitogenic and anti-apoptotic molecules. NK-22 cells are also found in mouse MALT and appear in the small intestine lamina propria during bacterial infection suggesting that NK-22 cells provide an innate source of IL-22 that may help constrain inflammation and protect mucosal sites.
We report the clinical description and molecular dissection of a new fatal human inherited disorder characterized by chronic auto-inflammation, invasive bacterial infections and muscular amylopectinosis. Patients from two kindreds carried biallelic loss-of-expression and loss-of-function mutations in HOIL1, a component the linear ubiquitination chain assembly complex (LUBAC). These mutations resulted in impairment of LUBAC stability. NF-κB activation in response to interleukin-1β (IL-1β) was compromised in the patients’ fibroblasts. By contrast, the patients’ mononuclear leukocytes, particularly monocytes, were hyperresponsive to IL-1β. The consequences of human HOIL-1 and LUBAC deficiencies for IL-1β responses thus differed between cell types, consistent with the unique association of auto-inflammation and immunodeficiency in these patients. These data suggest that LUBAC regulates NF-κB-dependent IL-1β responses differently in different cell types.
Notch2 mutations represent the most frequent lesion in splenic marginal zone lymphoma.
Splenic marginal zone lymphoma (SMZL) is a B cell malignancy of unknown pathogenesis, and thus an orphan of targeted therapies. By integrating whole-exome sequencing and copy-number analysis, we show that the SMZL exome carries at least 30 nonsilent gene alterations. Mutations in NOTCH2, a gene required for marginal-zone (MZ) B cell development, represent the most frequent lesion in SMZL, accounting for ∼20% of cases. All NOTCH2 mutations are predicted to cause impaired degradation of the NOTCH2 protein by eliminating the C-terminal PEST domain, which is required for proteasomal recruitment. Among indolent B cell lymphoproliferative disorders, NOTCH2 mutations are restricted to SMZL, thus representing a potential diagnostic marker for this lymphoma type. In addition to NOTCH2, other modulators or members of the NOTCH pathway are recurrently targeted by genetic lesions in SMZL; these include NOTCH1, SPEN, and DTX1. We also noted mutations in other signaling pathways normally involved in MZ B cell development, suggesting that deregulation of MZ B cell development pathways plays a role in the pathogenesis of ∼60% SMZL. These findings have direct implications for the treatment of SMZL patients, given the availability of drugs that can target NOTCH, NF-κB, and other pathways deregulated in this disease.
Nectins and Nectin-like molecules (Necls) play a critical role in cell polarity within epithelia and in the nervous and reproductive systems. Recently, immune receptors specific for Nectins/Necls have been described. Since expression and distribution of Nectins/Necls is often subverted during tumorigenesis, it has been suggested that the immune system may use these receptors to recognize and eliminate tumors. Here we describe a novel immunoreceptor, WUCAM, which is expressed on human follicular B helper T cells (Tfh) and binds a Nectin/Necl family member, the poliovirus receptor (PVR), under both static and flow conditions. Futhermore, we demonstrate that PVR is abundantly expressed by follicular dendritic cells (FDC) within the germinal center. These results reveal a novel molecular interaction that mediates adhesion of Tfh to FDC and provide the first evidence that immune receptors for Nectins/Necls may be involved the generation of T cell-dependent antibody responses.
Human; nectins; follicular B helper T cells; follicular dendritic cells
We evaluated the expression of human trophoblast cell-surface marker (Trop-2) in endometrial endometrioid carcinoma (EEC) and the potential application of hRS7, a humanized monoclonal anti-Trop-2 antibody, as a therapeutic agent against poorly-differentiated EEC.
Trop-2 expression was evaluated by immunohistochemistry in 131 EEC with different degrees of differentiation and 32 normal endometrial controls (NEC). Trop-2 expression was also evaluated by real-time polymerase-chain-reaction (qRT-PCR) and flow cytometry in 3 primary EEC cell lines derived from patients harboring poorly-differentiated EEC. Finally, sensitivity of G3 EEC cell lines to hRS7 antibody-dependent cellular-cytotoxicity (ADCC) was tested in standard 5-hours 51Cr-release assays.
Trop-2 expression was detected in 126 of 131 (96.2%) EEC samples. Tumor tissues showed markedly increased Trop-2 positivity as compared to NEC (p=0.001). Trop-2 expression was significantly higher in all grades of EEC vs. NEC. G3 tumors displayed significantly stronger Trop-2 immunostaining compared to G1 EEC (p=0.01). High Trop-2 expression by qRT-PCR and flow cytometry was found in one G3 EEC primary cell line (EEC-ARK-1). Unlike Trop-2-negative EEC cell lines, EEC-ARK-1 was found highly sensitive to hRS7-mediated ADCC in vitro (range of killing: 33.9% to 50.6%) (p=0.004). Human serum did not significantly inhibit hRS7-mediated-cytotoxicity against EEC-ARK-1 (p= 0.773).
Trop-2 is highly expressed in EEC and its expression is significantly higher in poorly-differentiated EEC when compared to well-differentiated EEC. Primary G3 EEC overexpressing Trop-2 are highly sensitive to hRS7-mediated cytotoxicity in vitro. hRS7 may represent a novel therapeutic agent for the treatment of high-grade EEC refractory to standard treatment modalities.
Endometrial cancer; Endometrioid adenocarcinoma; Immunotherapy; Natural Killer Cells; Trop-2 protein
Endometrial cancer is the most common gynecologic malignancy in developed countries. Trop-2 is a glycoprotein involved in cellular signal transduction and is differentially overexpressed relative to normal tissue in a variety of human adenocarcinomas, including endometrioid endometrial carcinomas (EEC). Trop-2 overexpression has been proposed as a marker for biologically aggressive tumor phenotypes.
Trop-2 protein expression was quantified using tissue microarrays consisting of formalin-fixed paraffin-embedded specimens from 118 patients who underwent surgical staging from 2001–9 by laparotomy for EEC. Clinicopathologic characteristics including age, stage, grade, lymphovascular space invasion, and medical comorbidities were correlated with immunostaining score. Univariate and multivariate analyses were performed for overall survival, disease-free survival, and progression-free survival in relation to clinical parameters and Trop-2 protein expression.
Clinical outcome data were available for 103 patients. Strong Trop-2 immunostaining was significantly associated with higher tumor grade (p=0.02) and cervical involvement (p<0.01). Univariate analyses showed a significant association with reduced disease-free survival (DFS) (p=0.01), and a trend towards significance for overall and progression-free survival (p=0.06 and p=0.05, respectively). Multivariate analyses revealed Trop-2 overexpression and advanced FIGO stage to be independent prognostic factors for poor DFS (p=0.04 and p <0.001, respectively).
Trop-2 protein overexpression is significantly associated with higher tumor grade and serves as an independent prognostic factor for DFS in endometrioid endometrial cancer.
Endometrioid endometrial cancer; Trop-2; TACSTD2; Tissue microarrays; Prognostic factor
The prevalence of Borrelia burgdorferi sensu lato DNA in diagnostic tissue samples from fresh cutaneous biopsies of 98 primary cutaneous lymphomas and 19 normal skin controls was investigated. A pathogenic role of B. burgdorferi in primary cutaneous B- and T-cell lymphomas from areas nonendemic for this microorganism is not supported nor is the consequent rationale for antibiotic therapy in these patients.
Borrelia burgdorferi has been variably associated with different forms of primary cutaneous lymphoma. Differences in prevalence rates among reported studies could be a result of geographic variability or heterogeneity in the molecular approaches that have been employed. In the present study, we investigated the prevalence of Borrelia burgdorferi sensu lato DNA in diagnostic tissue samples from fresh cutaneous biopsies of 98 primary cutaneous lymphomas and 19 normal skin controls. Three different polymerase chain reaction (PCR) protocols targeting the hbb, flagellin, and Osp-A genes were used. Direct sequencing of both sense and antisense strands of purified PCR products confirmed the specificity of the amplified fragments. Sequence specificity was assessed using the Basic Local Alignment Search Tool, and MultAlin software was used to investigate the heterogeneity of target gene sequences across the different samples.
Borrelia DNA was not detected in 19 controls, 23 cases of follicular lymphoma, 31 cases of extranodal marginal zone lymphoma, or 30 cases of mycosis fungoides. A single case of 14 diffuse large B-cell lymphoma cases was positive for B. burgdorferi.
This study does not support a pathogenic role of B. burgdorferi in primary cutaneous B- and T-cell lymphomas from areas nonendemic for this microorganism and the consequent rationale for the adoption of antibiotic therapy in these patients.
Cutaneous lymphoma; Borrelia burgdorferi; hbb gene; Mycosis fungoides; MALT lymphoma; Diffuse large B-cell lymphoma of leg type; Infections
CCRL2 is a heptahelic transmembrane receptor that shows the highest degree of homology with CCR1, an inflammatory chemokine receptor. CCRL2 mRNA was rapidly (30 min) and transiently (2-4 hrs) regulated during dendritic cell (DC) maturation. Protein expression paralleled RNA regulation. In vivo, CCRL2 was expressed by activated DC and macrophages, but not by eosinophils and T cells. CCRL2−/− mice showed normal recruitment of circulating DC into the lung but a defective trafficking of antigen-loaded lung DC to mediastinal lymph nodes. This defect was associated to a reduction in lymph node cellularity and reduced priming of Th2 response. CCRL2−/− mice were protected in a model of OVA-induced airway inflammation with reduced leukocyte recruitment in the BAL (eosinophils and mononuclear cells) and reduced production of the Th2 cytokines IL-4 and IL-5 and chemokines CCL11 and CCL17. The central role of CCRL2 deficiency in DC was supported by the fact that adoptive transfer of CCRL2−/− antigen-loaded DC in wild type animals recapitulated the phenotype observed in knock out mice. These data show a nonredundant role of CCRL2 in lung DC trafficking and propose a role for this receptor in the control of excessive airway inflammatory responses.
High-risk neuroblastoma is a severe pediatric tumor characterized by poor prognosis. Understanding the molecular mechanisms involved in tumor development and progression is strategic for the improvement of pharmacological therapies. Notch was recently proposed as a pharmacological target for the therapy of several cancers and is emerging as a new neuroblastoma-related molecular pathway. However, the precise role played by Notch in this cancer remains to be studied extensively. Here, we show that Notch activation by the Jagged1 ligand enhances the proliferation of neuroblastoma cells, and we propose the possible use of Notch-blocking γ-secretase inhibitors (GSIs) in neuroblastoma therapy. Two different GSIs, Compound E and DAPT, were tested alone or in combination with 13-cis retinoic acid (RA) on neuroblastoma cell lines. SH-SY5Y and IMR-32 cells were chosen as paradigms of lower and higher malignancy, respectively. Used alone, GSIs induced complete cell growth arrest, promoted neuronal differentiation, and significantly reduced cell motility. The combination of GSIs and 13-cis RA resulted in the enhanced growth inhibition, differentiation, and migration of neuroblastoma cells. In summary, our data suggest that a combination of GSIs with 13-cis RA offers a therapeutic advantage over a single agent, indicating a potential novel therapy for neuroblastoma.
γ-secretase inhibitors; 13-cis retinoic acid; cell migration; differentiation; neuroblastoma
A phase I/II trial was undertaken to determine maximum tolerated dose (MTD), toxicity, clinical efficacy and biological activity of bortezomib in patients with advanced stage primary or post-polycythemia vera/post-essential thrombocythemia myelofibrosis (MF). Bortezomib (0.8, 1.0, or 1.3 mg/m2) was administered on days 1, 4, 8, and 11 by intravenous push to patients previously resistant to at least one line of therapy, or with an intermediate/high risk IWG’s score . Therapy was repeated every 28 days for 6 cycles. At 1.3 mg/m2 dose, one of six patients experienced a dose limiting toxicity, and this was determined to be the MTD. Neither remissions or clinical improvements were recorded in 16 patients treated at this dose level, fulfilling the early stopping rule in the Simon two-stage study design. Major toxicity was on thrombocytopenia. In 9 out of 15 patients bortezomib proved able to reduce bone marrow vessel density. However, the agent was associated with worsening of markers of disease activity, like enhancement of hematopoietic CD34-positive progenitor cell mobilization, WT-1 gene expression in mononuclear cells, and down-regulation of CXCR4 expression on CD34-positive cells. Occurrence of both beneficial and detrimental biological effects claims further investigation on the mechanisms of the drug in MF.
Hypomorphic RAG mutations, leading to limited V(D)J rearrangements, cause Omenn syndrome (OS), a peculiar severe combined immunodeficiency associated with autoimmune-like manifestations. Whether B cells play a role in OS pathogenesis is so far unexplored. Here we report the detection of plasma cells in lymphoid organs of OS patients, in which circulating B cells are undetectable. Hypomorphic Rag2R229Q knock-in mice, which recapitulate OS, revealed, beyond severe B cell developmental arrest, a normal or even enlarged compartment of immunoglobulin-secreting cells (ISC). The size of this ISC compartment correlated with increased expression of Blimp1 and Xbp1, and these ISC were sustained by elevated levels of T cell derived homeostatic and effector cytokines. The detection of high affinity pathogenic autoantibodies toward target organs indicated defaults in B cell selection and tolerance induction. We hypothesize that impaired B cell receptor (BCR) editing and a serum B cell activating factor (BAFF) abundance might contribute toward the development of a pathogenic B cell repertoire in hypomorphic Rag2R229Q knock-in mice. BAFF-R blockade reduced serum levels of nucleic acid-specific autoantibodies and significantly ameliorated inflammatory tissue damage. These findings highlight a role for B cells in OS pathogenesis.
The contribution of B cells to the pathology of Omenn syndrome and leaky severe combined immunodeficiency (SCID) has not been previously investigated. We have studied a mut/mut mouse model of leaky SCID with a homozygous Rag1 S723C mutation that impairs, but does not abrogate, V(D)J recombination activity. In spite of a severe block at the pro–B cell stage and profound B cell lymphopenia, significant serum levels of immunoglobulin (Ig) G, IgM, IgA, and IgE and a high proportion of Ig-secreting cells were detected in mut/mut mice. Antibody responses to trinitrophenyl (TNP)-Ficoll and production of high-affinity antibodies to TNP–keyhole limpet hemocyanin were severely impaired, even after adoptive transfer of wild-type CD4+ T cells. Mut/mut mice produced high amounts of low-affinity self-reactive antibodies and showed significant lymphocytic infiltrates in peripheral tissues. Autoantibody production was associated with impaired receptor editing and increased serum B cell–activating factor (BAFF) concentrations. Autoantibodies and elevated BAFF levels were also identified in patients with Omenn syndrome and leaky SCID as a result of hypomorphic RAG mutations. These data indicate that the stochastic generation of an autoreactive B cell repertoire, which is associated with defects in central and peripheral checkpoints of B cell tolerance, is an important, previously unrecognized, aspect of immunodeficiencies associated with hypomorphic RAG mutations.
Langerhans cells (LC) represent a well characterized subset of dendritic cells located in the epidermis of skin and mucosae. In vivo, they originate from resident and blood-borne precursors in the presence of keratinocyte-derived TGFβ. Ιn vitro, LC can be generated from monocytes in the presence of GM-CSF, IL-4 and TGFβ. However, the signals that induce LC during an inflammatory reaction are not fully investigated. Here we report that Activin A, a TGFβ family member induced by pro-inflammatory cytokines and involved in skin morphogenesis and wound healing, induces the differentiation of human monocytes into LC in the absence of TGFβ. Activin A-induced LC are Langerin+, Birbeck granules+, E-cadherin+, CLA+ and CCR6+ and possess typical APC functions. In human skin explants, intradermal injection of Activin A increased the number of CD1a+ and Langerin+ cells in both the epidermis and dermis by promoting the differentiation of resident precursor cells. High levels of Activin A were present in the upper epidermal layers and in the dermis of Lichen Planus biopsies in association with a marked infiltration of CD1a+ and Langerin+ cells. This study reports that Activin A induces the differentiation of circulating CD14+ cells into LC. Since Activin A is abundantly produced during inflammatory conditions which are also characterized by increased numbers of LC, we propose that this cytokine represents a new pathway, alternative to TGFβ, responsible for LC differentiation during inflammatory/autoimmune conditions.
To determine the role of interferon-alpha in controlling HIV infection we phenotypically and functionally analyzed circulating plasmacytoid dendritic cells (pDC), which are known to be the highest interferon-alpha producing cells, in 33 perinatally infected HIV+ patients undergoing standard antiretroviral therapy.
Circulating pDC were identified by flow cytometry using anti-BDCA-2 monoclonal antibody and by measuring BDCA-2 mRNA by real-time PCR, while tissue-resident pDC were identified by immunohistochemistry. mRNA for interferon-alpha and MxA, a gene that is specifically induced by interferon-alpha, was quantified in peripheral blood cells by real-time PCR, while serum interferon-alpha protein was measured by ELISA.
While median values of pDC, both in terms of percentage and absolute number, were not statistically different from age-matched controls, interferon-alpha mRNA was increased in HIV-infected patients. However, in a group of patients with long disease duration, having a low number of both pDC and CD4+ lymphocytes and a significant increase of serum interferon-alpha, MxA mRNA was produced at high level and its expression directly correlated with HIV RNA copy numbers. Furthermore in patients displaying a low CD4+ blood cell count, a severe depletion of pDC in the tonsils could be documented.
HIV replication unresponsive to antiretroviral treatment in perinatal-infected patients with advanced disease and pDC depletion may lead to interferon-alpha expression and subsequent induction of MxA mRNA. Thus, the latter measurement may represent a valuable marker to monitor the clinical response to therapy in HIV patients.
Rag enzymes are the main players in V(D)J recombination, the process responsible for rearrangement of TCR and Ig genes. Hypomorphic Rag mutations in humans, which maintain partial V(D)J activity, cause a peculiar SCID associated with autoimmune-like manifestations, Omenn syndrome (OS). Although a deficient ability to sustain thymopoiesis and to produce a diverse T and B cell repertoire explains the increased susceptibility to severe infections, the molecular and cellular mechanisms underlying the spectrum of clinical and immunological features of OS remain poorly defined. In order to better define the molecular and cellular pathophysiology of OS, we generated a knockin murine model carrying the Rag2 R229Q mutation previously described in several patients with OS and leaky forms of SCID. These Rag2R229Q/R229Q mice showed oligoclonal T cells, absence of circulating B cells, and peripheral eosinophilia. In addition, activated T cells infiltrated gut and skin, causing diarrhea, alopecia, and, in some cases, severe erythrodermia. These findings were associated with reduced thymic expression of Aire and markedly reduced numbers of naturally occurring Tregs and NKT lymphocytes. In conclusion, Rag2R229Q/R229Q mice mimicked most symptoms of human OS; our findings support the notion that impaired immune tolerance and defective immune regulation are involved in the pathophysiology of OS.
Chemerin is a chemotactic agent that was recently identified as the ligand of ChemR23, a serpentine receptor expressed by activated macrophages and monocyte-derived dendritic cells (DCs). This paper shows that blood plasmacytoid and myeloid DCs express functional ChemR23. Recombinant chemerin induced the transmigration of plasmacytoid and myeloid DCs across an endothelial cell monolayer. In secondary lymphoid organs (lymph nodes and tonsils), ChemR23 is expressed by CD123+ plasmacytoid DCs and by CD1a+ DC-SIGN+ DCs in the interfollicular T cell area. ChemR23+ DCs were also observed in dermis from normal skin, whereas Langerhans cells were negative. Chemerin expression was selectively detected on the luminal side of high endothelial venules in secondary lymphoid organs and in dermal endothelial vessels of lupus erythematosus skin lesions. Chemerin+ endothelial cells were surrounded by ChemR23+ plasmacytoid DCs. Thus, ChemR23 is expressed and functional in plasmacytoid DCs, a property shared only by CXCR4 among chemotactic receptors. This finding, together with the selective expression of the cognate ligand on the luminal side of high endothelial venules and inflamed endothelium, suggests a key role of the ChemR23/chemerin axis in directing plasmacytoid DC trafficking.
Omenn syndrome is a severe primary immunodeficiency with putative autoimmune manifestations of the skin and gastrointestinal tract. The disease is caused by hypomorphic mutations in recombination-activating genes that impair but do not abolish the process of VDJ recombination, leading to the generation of autoreactive T cells with a highly restricted receptor repertoire. Loss of central tolerance in genetically determined autoimmune diseases, e.g., autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy, is associated with defective expression by medullary thymic epithelial cells of AIRE, the transcription activator that induces thymic expression of tissue-specific antigens. Analysis of AIRE expression in the thymi of 2 Omenn syndrome patients and 1 SCID patient, by real-time RT-PCR and immunohistochemistry, demonstrated a profound reduction in the levels of AIRE mRNA and protein in patients as compared with a normal control subject. Lack of AIRE was associated with normal or even increased levels of keratin and lymphotoxin-β receptor mRNAs, while mRNAs of the self-antigens insulin, cytochrome P450 1a2, and fatty acid–binding protein were undetectable in thymi from immunodeficiency patients. These results demonstrate that deficiency of AIRE expression is observed in severe immunodeficiencies characterized by abnormal T cell development and suggest that in Omenn syndrome, the few residual T cell clones that develop may escape negative selection and thereafter expand in the periphery, causing massive autoimmune reactions.
Plasmacytoid dendritic cells are present in lymphoid and nonlymphoid tissue and contribute substantially to both innate and adaptive immunity. Recently, we have described several monoclonal antibodies that recognize a plasmacytoid dendritic cell-specific antigen, which we have termed BDCA-2. Molecular cloning of BDCA-2 revealed that BDCA-2 is a novel type II C-type lectin, which shows 50.7% sequence identity at the amino acid level to its putative murine ortholog, the murine dendritic cell–associated C-type lectin 2. Anti–BDCA-2 monoclonal antibodies are rapidly internalized and efficiently presented to T cells, indicating that BDCA-2 could play a role in ligand internalization and presentation. Furthermore, ligation of BDCA-2 potently suppresses induction of interferon α/β production in plasmacytoid dendritic cells, presumably by a mechanism dependent on calcium mobilization and protein-tyrosine phosphorylation by src-family protein-tyrosine kinases. Inasmuch as production of interferon α/β by plasmacytoid dendritic cells is considered to be a major pathophysiological factor in systemic lupus erythematosus, triggering of BDCA-2 should be evaluated as therapeutic strategy for blocking production of interferon α/β in systemic lupus erythematosus patients.
interferon type I; monoclonal antibodies; magnetic cell sorting; interferon inducers; systemic lupus erythematosus