Enhanced type I interferon signalling promotes Th1-biased inflammation in cutaneous lupus erythematosus

Recent studies have suggested that type I interferons (IFN) play a role in the pathogenesis of lupus erythematosus (LE), an autoimmune disease of unknown aetiology. Natural interferon-producing plasmacytoid cells have been demonstrated in cutaneous LE (CLE) lesions, along with elevated levels of IFN-alpha mRNA. The hypothesis in the current study was that local production of type I IFNs in CLE induces Th1-biased inflammation via induction of IFN-inducible chemokines such as IP10/CXCL10 leading to the recruitment of chemokine receptor CXCR3 expressing T-cells into skin lesions. Skin biopsies from 21 patients suffering from different types of active cutaneous LE were analysed for the expression of MxA, a protein specifically induced by type I interferons, the IFN-inducible protein IP10/CXCL10, and the chemokine receptor CXCR3, characteristic for Th1 cells, by immunohistochemistry. Additionally, peripheral CD4+ and CD8+ T-cells were investigated for the expression of MxA and CXCR3 by flow cytometry. Cutaneous LE lesions were characterized by strong expression of MxA indicating the induction of localized type I IFN signalling in the skin. Large numbers of infiltrating CXCR3 positive lymphocytes were detected in CLE skin lesions, and correlated closely with lesional MxA expression (epidermis: Spearman's rho = 0.56, p < 0.001; dermis: rho = 0.82, p < 0.001). Intracellular MxA levels of circulating CD4+ and CD8+ T-cells were significantly enhanced in patients with active CLE lesions. The percentage of peripheral T-cells expressing CXCR3 was significantly decreased in specific CLE subtypes. Expression of IP10/CXCL10 in the epidermis links type I IFN signalling and recruitment of CXCR3+ T cells. These results suggest an important role for type I interferon signalling in the pathogenesis of cutaneous lupus erythematosus. It is proposed that type I IFNs induce a Th1-biased inflammatory immune response, with recruitment of CXCR3-expressing T-lymphocytes into the skin.     

HIV-infected cells are major inducers of plasmacytoid dendritic cell interferon production, maturation, and migration

Plasmacytoid dendritic cells (PDC), natural type-1 interferon (IFN) producing cells, could play a role in the innate anti-HIV immune response. Previous reports indicated that PDC IFN production is induced by HIV. Our results show a more robust IFN induction when purified PDC (>95%) were exposed to HIV-infected cells. This effect was not observed with non-viable cells, DNA, and RNA extracted from infected cells, and viral proteins. The response was blocked by anti-CD4 and neutralizing anti-gp120 antibodies as well as soluble CD4. IFN induction by HIV-infected cells was also prevented by low-dose chloroquine, which inhibits endosomal acidification. PDC IFN release resulted in reduced HIV production by infected CD4+ cells, supporting an anti-HIV activity of PDC. Stimulated CD4+ cells induced PDC activation and maturation; markers for PDC migration (CCR7) were enhanced by HIV-infected CD4+ cells only. This latter finding could explain the decline in circulating PDC in HIV-infected individuals.     

Plasmacytoid dendritic cells prime IFN-gamma-secreting melanoma-specific CD8 lymphocytes and are found in primary melanoma lesions

Plasmacytoid dendritic cells (PDC) are a small population of leukocytes specialized in the production of type I IFN. It has been shown that PDC have a potent T cell stimulatory capacity in allogeneic mixed lymphocyte reaction, However, their role in initiating primary immune responses remains elusive. We report that blood PDC efficiently prime naive CD8(+) lymphocytes specific for the melan-A(26-35) epitope to become IFN-gamma producing cells in vitro. In addition, we found that CD40L-stimulated PDC induce expression on primed melan-A-specific T cells of cutaneous lymphocyte antigen and L-selectin (CD62L), homing receptors that allow the migration of effector cells to the inflamed skin. Finally, we show that PDC can be found in the peri-tumoral area of most primary cutaneous melanomas in vivo and that type I IFN-containing supernatants derived from PDC increase melanoma cell surface expression of CD95 and MHC class I and class II molecules in vitro. Our results suggest a new immunomodulatory role for tissue infiltrating PDC, which may prime tumor-specific T cell responses and affect tumor growth via soluble factors.     

CD40 on salivary gland epithelial cells: high constitutive expression by cultured cells from Sjögren's syndrome patients indicating their intrinsic activation

CD40 has been identified in an expanding list of haematopoietic and non‐haematopoietic cells and has received an increased interest based on its role in a variety of cell‐mediated responses and its potential to participate in the pathogenesis of chronic inflammatory disorders. Sjögren’s syndrome (SS) is an autoimmune exocrinopathy, which is characterized by chronic lymphocytic infiltration of exocrine glands and aberrant activation of epithelial tissues. We studied the expression of CD40 protein in cultured non‐neoplastic salivary gland epithelial cell (SGEC) lines as well as in minor SG biopsies obtained from 17 SS patients and 12 controls. Immunocytochemical and flow cytometric analyses had revealed the occurrence of constitutively expressed CD40 molecules on the surface of long‐term cultured SGEC lines, which could be further induced by interferon‐gamma (IFN‐γ) and IL‐1β cytokines, but not tumour necrosis factor‐alpha (TNF‐α), IL‐4, IL‐6, granulocyte‐macrophage colony‐stimulating factor (GM‐CSF) or IFN‐α. Triggering of SGEC through CD40 enhanced the surface expression of the adhesion molecule intercellular adhesion molecule‐1 (ICAM‐1)/CD54, but not MHC class I and class II (HLA‐DR) molecules. Spontaneous CD40 expression was significantly higher in SGEC lines derived from SS patients, compared with controls (P < 0·001), which is suggestive of their intrinsically activated status. In SG biopsies, CD40 was constitutively expressed by lymphocytes, ductal epithelial cells and endothelial cells but not by other glandular cell types, such as acinar cells, myoepithelial cells and fibroblasts. In addition, CD40L staining was also detected in 30–50% of the infiltrating lymphocytes in the biopsies of SS patients. Our findings indicate the immunoregulatory potential of SGEC and lend further support to a model of intrinsic activation in salivary epithelia in SS, whereby these cells actively participate in the induction and maintenance of lymphocytic infiltrates of patients.     

Infiltration of cytotoxic T cells in drug-induced cutaneous eruptions

BACKGROUND: Previous in vitro data indicate that perforin containing drug-specific cytotoxic T cells are involved in cutaneous drug reactions. OBJECTIVE: The aim of this study was to investigate the in situ expression of perforin and granzyme B together with the nature of the inflammatory infiltrate in acute drug-induced exanthem. Furthermore, expression of interleukin (IL)-12 and interferon (IFN)-gamma, which are known to stimulate cytotoxic T cells, was investigated. METHODS: Skin biopsy specimens were obtained from 10 patients with a generalized maculopapular exanthem and from nine controls with normal skin. Expression of CD3, CD4, CD8, CD56, CD1a, CD68, CD25, HLA-DR, CD54, perforin, granzyme B, IL-12 and IFNgamma was analysed using immunohistochemistry. RESULTS: In contrast to the controls, the skin of patients with an exanthem was mainly infiltrated by T cells (CD4 > CD8) and showed a marked enhancement of perforin and granzyme B immunostaining. Double immunostaining revealed that perforin and granzyme B were expressed in both CD4+ and CD8+ cells, which were partly located at the dermoepidermal junction and in the epidermis. In addition, strong immunreactivity for IL-12 and IFNgamma was observed in the mononuclear cells infiltrate, indicating that these cytokines may be important in activation of these cytotoxic T cells. CONCLUSION: The increased numbers of perforin and granzyme B containing T cells infiltrating the dermoepidermal junction may contribute to the damage of epidermal cells, which is frequently observed as a typical feature of interface dermatitis in drug-induced exanthem. Our data provide further evidence that cytotoxic T cells play an essential role in cutaneous drug reactions.     

Engagement of BDCA-2 blocks TRAIL-mediated cytotoxic activity of plasmacytoid dendritic cells

Plasmacytoid dendritic cells (PDC) are a functionally distinct lineage of dendritic cells characterized by the release of large amounts of type I interferon (IFN I). IFN I release is efficiently triggered by viral infection and modulates several aspects of immune reactions including the activation of cytotoxic mechanisms finalized to the elimination of infected cells. In this study, we report that TLR7 and TLR9 ligands can induce the secretion of biologically active TNF-related apoptosis-inducing ligand (TRAIL) by PDC. Accordingly, PDC supernatant is endowed with TRAIL-mediated cytotoxic activity when tested on a TRAIL-sensitive Jurkat cell line. TRAIL production is only partially dependent on the autocrine production of IFN I as documented by the use of a blocking anti-IFNRA antibody and the stimulation with exogenous IFN I. Importantly, both TRAIL secretion and cytotoxic activity of PDC supernatants are completely abolished by BDCA2 ligation. These results provide further insights into the biological role of BDCA-2 and document a negative regulatory pathway of PDC cytotoxic activity that may be relevant in pathological situations such as tumors and autoimmune diseases.     

Trichostatin A blocks type I interferon production by activated plasmacytoid dendritic cells

Plasmacytoid dendritic cells (PDC) represent the main type I interferon (IFN-I) producing cells. Emerging evidence supports a role for IFN-I in autoimmune diseases. Given the central role of PDC in the pathogenesis of systemic lupus erythematosus (SLE), we investigated the effect of Trichostatin A (TSA), a prototypic histone deacetylase inhibitor, on PDC activation. TSA inhibited the production of IFN-I, TRAIL and of the pro-inflammatory cytokines TNFα and IL-6 by CpG-activated PDC. These effects were associated with the inhibition of IFN Regulatory Factor (IRF)-7 nuclear translocation. Furthermore, TSA was also effective in inhibiting the production of IFNα by PDC cultured in vitro in the presence of serum obtained from SLE patients. This study describes a new level of regulation of immune responses by histone deacetylase inhibitors and defines the molecular basis for new strategies to be exploited in the treatment of autoimmune diseases.     

Differential Expression of CD30 on CD3 T Lymphocytes in Patients with Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE) is an autoimmune systemic disease caused as a result of an imbalance of Th1‐/Th2‐type cytokines. The soluble form of CD30 (CD30s) released from peripheral blood cells has been described as a marker of active disease in Th2‐type immune response as in SLE. However, the expression of CD30 on CD3 T lymphocytes from patients with SLE has not been studied yet. Therefore, we have addressed our study to attempt this issue, studying CD30 expression by flow cytometry on CD3 T lymphocytes and CD4/CD8 subsets in samples from SLE patients mainly with lupus nephritis. In parallel, we have determined the production of the cytokines IL‐4 (Th2), IFNγ (Th1), IL‐10 and TGFβ by intracellular staining. Differences between positive CD30 T cells in healthy controls and patients with SLE were found, with a higher percentage of CD30‐expressing T cells in patients with SLE (P = 0.001). In contrast to healthy controls, CD30 was mainly expressed on CD8 T cells from patients with SLE. The intracellular cytokine staining showed that TGFβ is the main cytokine expressed in CD3 T cells from patients with SLE. In addition to this, we have found a positive correlation between CD30‐expressing T cells and IL‐4, IFNγ, and immunosuppressive cytokines (IL‐10 and TGFβ) (P < 0.05). These results suggest that CD30 could play a role in the pathogenesis of SLE and its expression on CD3 T lymphocytes is not restricted only to Th2‐type response.     

Plasmacytoid dendritic cells induce a distinct cytokine pattern in virus-specific CD4+ memory T cells that is modulated by CpG oligodeoxynucleotides

Inherent properties of dendritic cell (DC) subsets are important in the regulation of naïve T‐cell differentiation (e.g. Th1 versus Th2 cells), whereas effector memory T cells are believed to produce a fixed cytokine repertoire independent of the type of antigen presenting cell. Here we show that two distinct human DC subsets, plasmacytoid DC (PDC) and myeloid CD11c+ DC, induced autologous mumps virus‐specific memory CD4⁺ T cells to produce markedly different cytokine patterns upon antigen stimulation. PDC stimulated the T cells to produce γ‐interferon (IFN‐γ) and interleukin‐(IL)‐10, whereas CD11c+ DC induced lower levels of IFN‐γ, virtually no IL‐10, but significant levels of IL‐5. Analysis of intracellular cytokine production showed simultaneous production of IL‐10 and IFN‐γ in mumps‐specific T cells activated by PDC, a cytokine pattern similar to that described for Th1‐like regulatory cells. Introduction of CpG oligodeoxynucleotides in PDC/T‐cell co‐cultures had synergistic effect on virus‐dependent IFN‐γ production, whereas the other cytokines remained unchanged. Together, our results show that the type of DC involved in reactivation of previously primed T cells may have significant impact on the resulting cytokine response and suggest that targeting of viral antigens and adjuvant to specific DC subsets should be considered in the design of therapeutic antiviral vaccines.     

Expression of cytotoxic proteins by neoplastic T cells in mycosis fungoides increases with progression from plaque stage to tumor stage disease

Granzyme B (GrB) and T-cell-restricted intracellular antigen (TIA-1) are cytotoxic proteins that are specifically expressed by cytotoxic CD4 or CD8 positive T cells and natural killer cells. Recent studies demonstrated frequent expression of GrB and TIA-1 by neoplastic cells in primary cutaneous CD30(+) large T-cell lymphomas and lymphomatoid papulosis but not in CD30(-) large T-cell lymphomas. In the present study, 74 biopsies from 54 patients with mycosis fungoides (MF) were investigated for the expression of GrB and TIA-1 using immunohistochemistry on paraffin sections. Staining of more than 10% of the neoplastic T cells for GrB or TIA-1 was considered positive. All but two follow-up biopsies had been obtained from patients without extracutaneous disease at the time of biopsy. Expression of TIA-1 and GrB was found in 33 (45%) and 14 (19%) of 74 MF biopsies, respectively. Comparison of biopsies from T3NoMo-stage MF (n = 27) and T2NoMo-stage MF (n = 45) showed increased expression of TIA-1 (55 versus 37%) and GrB (33 versus 9%) in T3NoMo-stage MF. Evaluation of multiple sequential biopsies from successive stages of MF also revealed an increase in the GrB/TIA-1 expression with tumor progression in five of eight cases. A clearcut relation between the expression of TIA-1 and/or GrB and the type of skin lesion biopsied was found. Considering all 74 biopsies, expression of TIA-1 and GrB was found in 18 of 50 (35%) and 5 of 50 (10%) patches or plaques, 9 of 16 (55%) and 3 of 16 (20%) tumors without blastic transformation, and 6 of 8 (75%) and 6 of 8 (75%) tumors with blastic transformation (defined as >50% blast cells). Correlation between GrB/TIA-1 expression in first diagnostic biopsies from patches or plaques from 40 patients with T2NoMo-stage MF and clinical follow-up data did not reveal differences in clinical behavior and survival between patients with (n = 14) or without (n = 26) expression of cytotoxic proteins, indicating that MF expressing cytotoxic proteins should not be considered as a separate group.     

A role for the B-cell CD74/macrophage migration inhibitory factor pathway in the immunomodulation of systemic lupus erythematosus by a therapeutic tolerogenic peptide

Systemic lupus erythematosus (SLE) is an autoimmune disease that involves dysregulation of B and T cells. A tolerogenic peptide, designated hCDR1, ameliorates disease manifestations in SLE‐afflicted mice. In the present study, the effect of treatment with hCDR1 on the CD74/macrophage migration inhibitory factor (MIF) pathway was studied. We report here that B lymphocytes from SLE‐afflicted mice express relatively elevated levels of CD74, compared with B cells from healthy mice. CD74 is a receptor found in complex with CD44, and it binds the pro‐inflammatory cytokine MIF. The latter components were also up‐regulated in B cells from the diseased mice, and treatment with hCDR1 resulted in their down‐regulation and in reduced B‐cell survival. Furthermore, up‐regulation of CD74 and CD44 expression was detected in brain hippocampi and kidneys, two target organs in SLE. Treatment with hCDR1 diminished the expression of those molecules to the levels determined for young healthy mice. These results suggest that the CD74/MIF pathway plays an important role in lupus pathology.     

Interferon-α regulates abnormally increased expression of RSAD2 in Th17 and Tfh cells in systemic lupus erythematosus patients

Systemic lupus erythematosus (SLE) is a chronic autoimmune disease that often involves abnormal activation of regulatory IFN genes and regulation of B cells by CD4⁺ T cells. Radical S-adenosyl methionine domain containing 2 (RSAD2) is a viral suppressor protein regulated by type I IFN, and it has been proven to play an important regulatory role in SLE. However, the mechanism by which RSAD2 participates in the pathogenesis of SLE is unclear. In this study, we observed higher expression levels of RSAD2 in CD4⁺ T-cell subsets from the peripheral blood of SLE patients than in those from healthy controls by bioinformatics analysis and validation experiments. We analyzed the expression of RSAD2 in CD4⁺ T cells of patients with SLE and other autoimmune diseases. In addition, we found that the expression of RSAD2 in CD4⁺ T cells might be regulated by IFN-α, and RSAD2 significantly affected the differentiation of Th17 cells and T follicular helper (Tfh) cells. Our findings underlined that RSAD2 may promote B-cell activation by promoting the differentiation of Th17 and Tfh cells in SLE patients, a process that is regulated by IFN-α.     

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‐α, either exogenously added or endogenously induced, suppressed the generation of CD4⁺ FoxP3^HI IFN‐γ^Neg activated Tregs (aTregs) while simultaneously promoting propagation of CD4⁺ FoxP3^Low/Neg IFN‐γ^Pos activated Teffs (aTeffs). We also showed that IFN‐α‐mediated inhibition of interleukin (IL)‐2 production may play an essential role in IFN‐α‐induced suppression of aTregs. In order to test our findings in a disease state with chronically elevated IFN‐α, 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‐α (such as is seen in an early antiviral response) may promote CD4 effector functions by delaying aTreg generation, but a chronic elevation of IFN‐α may tip the aTeff:aTreg balance towards aTeffs and autoimmunity.     

Ultraviolet light converts propranolol,a nonselective β‐blocker and potential lupus‐inducing drug,into a proinflammatory AhR ligand

UV light and some medications are known to trigger lupus erythematosus (LE). A common mechanism underlying the immunopathologic effect, resulting from exposure to these two seemingly unrelated factors, remains unknown. The aryl hydrocarbon receptor (AhR) plays a key role in the regulation of IL‐22 production in humans and can be activated by both xenobiotics and naturally occurring photoproducts. A significant expansion of Th17 and Th22 cells was observed in the peripheral blood of active systemic LE (SLE) patients, compared to inactive patients and controls. We also show that propranolol, a potential lupus‐inducing drug, induced stronger AhR activation in PBMCs of SLE patients than in those of controls. AhR agonist activity of propranolol was enhanced by UV light exposure. MS analysis of irradiated propranolol revealed the generation of a proinflammatory photoproduct. This compound behaves like the prototypic AhR ligand 6‐formylindolo[3,2‐b]carbazole, a cutaneous UV light‐induced tryptophan metabolite, both promoting IL‐22, IL‐8, and CCL2 secretion by T‐cells and macrophages. Finally, LE patients exhibit signs of cutaneous AhR activation that correlate with lesional expression of the same proinflammatory cytokines, suggesting a role for photometabolites in the induction of skin inflammation. The AhR might therefore represent a target for therapeutic intervention in LE.     

Interferon-α mRNA in Splenic CD11b+ Marginal Zone Macrophages of C4-Deficient Mice

The absence of early complement components (C1, C4 and C2 but not C3) is a predisposing factor for systemic lupus erythematosus (SLE). Recently, we demonstrated that, in C4‐deficient (C4 def.) mice, IgM‐containing immune complexes (IgM‐IC) are filtered by the splenic barrier of marginal zone macrophages (MZM), resulting in an increased immune response against antigens within these IgM‐IC, but this could not be observed in wildtype or C3 def. mice. We hypothesized that splenic CD11b⁺ MZM play an important role in the induction of autoimmunity, and we therefore analysed their cytokine profile after isolation with the help of magnetic antibody cell sorting. mRNA was isolated, and real‐time PCR was performed with specific primers for murine IFN‐γ (IFN‐γ), interleukin‐12 (IL‐12) and IFN‐α (IFN‐α). We observe a moderate increase of IL‐12 and IFN‐γ mRNA in CD11b⁺ cells of C4 def. mice compared to wildtype cells. Surprisingly, the concentration of IFN‐α mRNA is six times higher in C4 def. mice. Preliminary results suggest that mRNA in CD11b⁺ cells of C3 def. mice is even lower than that in wt. Six hours following i.v. application of 20 µg of a murine monoclonal IgM anti‐dsDNA antibody, production of IL‐12, IFN‐γ and IFN‐α mRNA is increased in CD11b⁺ cells of both C4 def. and wt mice. Several references described increased levels of INF‐α in patients with SLE. Dendritic cells are discussed as a major source of IFN‐α. Our observation that C4‐deficient, SLE‐susceptible mice demonstrate an increased spontaneous IFN‐α production by splenic CD11b⁺ marginal zone macrophages could be an early sign and a trigger for the development of SLE. This is supported by the fact that the absence of C3 is not a predisposing factor for SLE and our observation that C3 def. animals display low levels of IFN‐α mRNA.     

Lupus erythematosus cell in body fluids: A case report and review of literature

The diagnosis of systemic lupus erythematosus (SLE) has undergone radical change after the development of serological techniques. The in vitro demonstration of lupus erythematosus (LE) cell has less significance for the diagnosis of SLE in the present scenario. Although over the years, the spontaneous in vivo occurrence of LE cell in numerous body fluids as an initial presentation of SLE has been documented. The report of the presence of the LE cell can not only aid in the further workup of the patient but also suggest the involvement of a particular organ or body cavities by SLE. The morphology and mimickers of the LE cell should be cogitated and meticulous search of such cells should play an important role in the evaluation of body fluids. In our case, the patient presented at emergency with pericardial tamponade and cytological evaluation of the pericardial fluid demonstrated in vivo presence of LE cells. The serological work‐up then confirmed the case to be SLE. This report and review of literature wish to highlight the fact that this cell still plays a significant role even in the era of immunoassays.     

The natural interferon-alpha producing cells in systemic lupus erythematosus

Prolonged exposure of the immune system to type I interferons (IFN-alpha/beta/omega) in patients receiving IFN-alpha therapy frequently results in development of autoantibodies and autoimmune disease. This is attributed to the many immunostimulatory effects of these cytokines. Patients with the autoimmune disease systemic lupus erythematosus (SLE) have an ongoing IFN-alpha production. Recent studies of SLE demonstrated the presence of endogenous IFN-alpha inducers, acting specifically on natural IFN-alpha producing cells (NIPC), often termed plasmacytoid dendritic cells (PDC). These IFN-alpha inducers were potent, present at the blood level, and characterized as immune complexes that contained DNA and IgG as essential components. They were considered a likely reason for the activated IFN-alpha production in SLE, which, in turn, might be an important etiopathogenic factor. Here, we briefly review the biology of the type I IFN system, with emphasis on inducers, producing cells (especially NIPC/PDC), IFN-alpha actions, and target immune cells, which might be relevant in SLE. Based on such information and results from studies in SLE patients, we propose a hypothesis that explains how NIPC/PDC become activated and play a pivotal etiopathogenic role in SLE and perhaps also other autoimmune diseases. This hypothesis furthermore indicates new therapeutic targets.     

Plasmacytoid dendritic cells (natural interferon- alpha/beta-producing cells) accumulate in cutaneous lupus erythematosus lesions.

Plasmacytoid dendritic cell (P-DC) precursors in peripheral blood produce large amounts of interferon (IFN)-alpha/beta when triggered by viruses. However, when incubated with interleukin-3 and CD40 ligand, the same precursors differentiate into mature DCs that stimulate na?ve CD4(+) T cells to produce Th2 cytokines. We recently reported that P-DCs accumulate in nasal mucosa of experimentally induced allergic rhinitis, supporting a role for this DC subset in Th2-dominated inflammation. Here we examined whether P-DCs accumulate in cutaneous lesions of lupus erythematosus (LE), a disorder associated with increased IFN-alpha/beta production. Our results showed that P-DCs were present in 14 out of 15 tissue specimens of cutaneous LE lesions, but not in normal skin. Importantly, the density of P-DCs in affected skin correlated well (r(s) = 0.79,P < 0.0005) with the high number of cells expressing the IFN-alpha/beta-inducible protein MxA, suggesting that P-DCs produce IFN-alpha/beta locally. Accumulation of P-DCs coincided also with the expression of L-selectin ligand peripheral lymph node addressin on dermal vascular endothelium, adding further support to the notion that these adhesion molecules are important in P-DC extravasation to peripheral tissue sites. Together, our findings suggested that P-DCs are an important source of IFN-alpha/beta in cutaneous LE lesions and may therefore be of pathogenic importance.     

Tuberculin-induced delayed-type hypersensitivity reaction in a model of hu-PBMC-SCID mice grafted with autologous skin.

We have developed an animal model to study human delayed-type hypersensitivity reactions. Previous studies in humans have shown after tuberculin injection the presence of a mononuclear cell infiltration, with almost no eosinophils, associated with a preferential Th-1-type cytokine profile. Human skin graft obtained from tuberculin-reactive donors was grafted onto the back of severe combined immunodeficient mice. After healing, mice were reconstituted intraperitoneally with peripheral mononuclear cells. Tuberculin and diluent were injected intradermally, and skin biopsies were performed 72 hours later. Skin grafts were divided into two parts, one for immunohistochemistry and one for in situ hybridization studies. Immunohistochemistry was performed on cryostat sections using the alkaline phosphatase anti-alkaline phosphatase technique. In the tuberculin-injected sites as compared with the diluent-injected sites, there were significant increases in the number of CD45+ pan leukocytes and CD4+, CD8+, CD45RO+ T cells but not in CD68+ monocytes/macrophages and EG2 or MBP+ eosinophils. The activation markers CD25 and HLA-DR were up-regulated in the tuberculin-injected sites. In situ hybridization was performed using 35S-labeled riboprobes for interleukin (IL)-2, interferon (IFN)-gamma, IL-4, and IL-5. After tuberculin injection, a preferential Th-1-type cytokine profile was observed with significant increases in the numbers of IL-2 and IFN-gamma mRNA-expressing cells. These results are similar to those reported after tuberculin-induced delayed-type hypersensitivity in humans, suggesting that this model might be useful to study cutaneous inflammatory reaction.