Inna Novitskaya

Psoriasis is characterized by accumulation of immunostimulatory and Th1/Th17 cell-polarizing myeloid dendritic cells.

Myeloid dermal dendritic cells (DCs) accumulate in chronically inflamed tissues such as psoriasis. The importance of these cells for psoriasis pathogenesis is suggested by comparative T-cell and DC-cell counts, where DCs outnumber T cells. We have previously identified CD11c(+)-blood dendritic cell antigen (BDCA)-1(+) cells as the main resident dermal DC population found in normal skin. We now show that psoriatic lesional skin has two populations of dermal DCs: (1) CD11c(+)BDCA-1(+) cells, which are phenotypically similar to those contained in normal skin and (2) CD11c(+)BDCA-1(-) cells, which are phenotypically immature and produce inflammatory cytokines. Although BDCA-1(+) DCs are not increased in number in psoriatic lesional skin compared with normal skin, BDCA-1(-) DCs are increased 30-fold. For functional studies, we FACS-sorted psoriatic dermal single-cell suspensions to isolate these two cutaneous DC populations, and cultured them as stimulators in an allogeneic mixed leukocyte reaction. Both BDCA-1(+) and BDCA-1(-) myeloid dermal DC populations induced T-cell proliferation, and polarized T cells to become T helper 1 (Th1) and T helper 17 (Th17) cells. In addition, psoriatic dermal DCs induced a population of activated T cells that simultaneously produced IL-17 and IFN-gamma, which was not induced by normal skin dermal DCs. As psoriasis is believed to be a mixed Th17/Th1 disease, it is possible that induction of these IL-17(+)IFN-gamma(+) cells is pathogenic. These cytokines, the T cells that produce them, and the inducing inflammatory DCs may all be important new therapeutic targets in psoriasis.

Low Expression of the IL-23/Th17 Pathway in Atopic Dermatitis Compared to Psoriasis

The classical Th1/Th2 paradigm previously defining atopic dermatitis (AD) and psoriasis has recently been challenged with the discovery of Th17 T cells that synthesize IL-17 and IL-22. Although it is becoming evident that many Th1 diseases including psoriasis have a strong IL-17 signal, the importance of Th17 T cells in AD is still unclear. We examined and compared skin biopsies from AD and psoriasis patients by gene microarray, RT-PCR, immunohistochemistry, and immunofluorescence. We found a reduced genomic expression of IL-23, IL-17, and IFN-γ in AD compared with psoriasis. To define the effects of IL-17 and IL-22 on keratinocytes, we performed gene array studies with cytokine-treated keratinocytes. We found lipocalin 2 and numerous other innate defense genes to be selectively induced in keratinocytes by IL-17. IFN-γ had no effect on antimicrobial gene-expression in keratinocytes. In AD skin lesions, protein and mRNA expression of lipocalin 2 and other innate defense genes (hBD2, elafin, LL37) were reduced compared with psoriasis. Although AD has been framed by the Th1/Th2 paradigm as a Th2 polar disease, we present evidence that the IL-23/Th17 axis is largely absent, perhaps accounting for recurrent skin infections in this disease.

Identification of Cellular Pathways of “Type 1,” Th17 T Cells, and TNF- and Inducible Nitric Oxide Synthase-Producing Dendritic Cells in Autoimmune Inflammation through Pharmacogenomic Study of Cyclosporine A in Psoriasis

Therapeutic modulation of psoriasis with targeted immunosuppressive agents defines inflammatory genes associated with disease activity and may be extrapolated to a wide range of autoimmune diseases. Cyclosporine A (CSA) is considered a “gold standard” therapy for moderate-to-severe psoriasis. We conducted a clinical trial with CSA and analyzed the treatment outcome in blood and skin of 11 responding patients. In the skin, as expected, CSA modulated genes from activated T cells and the “type 1” pathway (p40, IFN-γ, and STAT-1-regulated genes). However, CSA also modulated genes from the newly described Th17 pathway (IL-17, IL-22, and downstream genes S100A12, DEFB-2, IL-1β, SEPRINB3, LCN2, and CCL20). CSA also affected dendritic cells, reducing TNF and inducible NO synthase (products of inflammatory TNF- and inducible NO synthase-producing dendritic cells), CD83, and IL-23p19. We detected 220 early response genes (day 14 posttreatment) that were down-regulated by CSA. We classified >95% into proinflammatory or skin resident cells. More myeloid-derived than activated T cell genes were modulated by CSA (54 myeloid genes compared with 11 lymphocyte genes), supporting the hypothesis that myeloid derived genes contribute to pathogenic inflammation in psoriasis. In circulating mononuclear leukocytes, in stark contrast, no inflammatory gene activity was detected. Thus, we have constructed a genomic signature of successful treatment of psoriasis which may serve as a reference to guide development of other new therapies. In addition, these data also identify new gene targets for therapeutic modulation and may be applied to wide range of autoimmune diseases.

Lesional dendritic cells in patients with chronic atopic dermatitis and psoriasis exhibit parallel ability to activate T-cell subsets

BACKGROUND Atopic dermatitis (AD) and psoriasis represent polar immune diseases. AD is a T(H)2/T(H)22-dominant disease, whereas psoriasis is considered a T(H)1/T(H)17 disease. Local immune deviation is suggested to be regulated by dendritic cell (DC)-induced T-cell polarization and recruitment of specific T-cell subsets by chemokines. Although the role of chemokines is well documented, the actual contribution of DCs to activate polar T-cell subsets in human subjects is still a matter of speculation. OBJECTIVE We sought to elucidate the significance of each cutaneous DC subset in disease-specific T-cell immune deviation. METHODS We performed a comprehensive analysis of major cutaneous resident (Langerhans cells and blood dendritic cell antigen 1-positive dermal DCs) and inflammatory (inflammatory dendritic epidermal cells and blood dendritic cell antigen 1-negative dermal DCs) DC subsets directly isolated from the lesional skin of patients with AD and those with psoriasis. RESULTS The ability of each DC subset to expand T(H)1, T(H)2, T(H)17, and T(H)22 subsets was similar between the 2 diseases, despite the association of both with accumulation of resident and inflammatory DCs. We also confirmed differential upregulation of chemokine expression in patients with AD (CCL17, CCL18, and CCL22) and psoriasis (CXCL1, IL-8, and CCL20). The expression of CCL17 and CCL22 was higher in Langerhans cells from patients with AD than from patients with psoriasis, whereas the opposite was observed for CXCL9 and CXCL10. CONCLUSION Our results suggest that DC polarity does not directly drive differential T-cell subset responses. Alternatively, disease-specific chemokines might recruit specific memory T-cell subsets into the skin, which in turn might be activated and expanded by DCs at the site of inflammation, maintaining differential immune polarity in these diseases.

Alefacept (anti-CD2) causes a selective reduction in circulating effector memory T cells (Tem) and relative preservation of central memory T cells (Tcm) in psoriasis

BackgroundAlefacept (anti-CD2) biological therapy selectively targets effector memory T cells (Tem) in psoriasis vulgaris, a model Type 1 autoimmune disease.MethodsCirculating leukocytes were phenotyped in patients receiving alefacept for moderate to severe psoriasis.ResultsIn all patients, this treatment caused a preferential decrease in effector memory T cells (CCR7- CD45RA-) (mean 63% reduction) for both CD4+ and CD8+ Tem, while central memory T cells (Tcm) (CCR7+CD45RA-) were less affected, and naïve T cells (CCR7+CD45RA+) were relatively spared. Circulating CD8+ effector T cells and Type 1 T cells (IFN-γ-producing) were also significantly reduced.ConclusionAlefacept causes a selective reduction in circulating effector memory T cells (Tem) and relative preservation of central memory T cells (Tcm) in psoriasis.

Novel Insight into the Agonistic Mechanism of Alefacept In Vivo: Differentially Expressed Genes May Serve as Biomarkers of Response in Psoriasis Patients

Alefacept is an LFA3-Ig fusion protein that binds to CD2 and is thought to inhibit T cell activation by antagonism of CD2 signaling or by lysis of CD2+ cells. Alefacept is potential future therapeutic for organ transplant recipients or graft-vs-host disease and is an approved therapeutic for psoriasis vulgaris, which is a T cell-mediated inflammatory disease. However, alefacept improves psoriasis in only ∼50% of patients treated for 12 wk. We studied the immunologic effects of alefacept in a group of psoriasis patients during treatment. We found that T cells, especially CD8+ T cells, were rapidly decreased in the peripheral circulation. Decreases in circulating T cells were not associated with induced apoptosis. Unexpectedly, in addition to suppression of inflammatory genes, we found a marked induction of mRNAs for STAT1, IL-8, and monokine induced by IFN-γ during the first day of treatment in PBMC. We confirmed the agonistic effects of alefacept in PBMC in vitro, which were similar to CD3/CD28 ligation on T cells. These data establish that alefacept activates gene expression programs in leukocytes and suggest that its therapeutic action may be as a mixed agonist/antagonist. Furthermore, responding patients to alefacept treatment show unique patterns of gene modulation. Whereas alefacept down-regulated TCRs CD3D and CD2 in responders, nonresponders reveal a higher expression of T cell activation genes such as CD69 in pretreatment PBMC. These finding suggest a potential basis for categorizing responders vs nonresponders at an early time point in treatment or before treatment of a broad range of proinflammatory diseases. This study 1) establishes alefacept as a novel CD2 agonist molecule for induction of leukocyte activation genes (prior work proposed its mechanism as a CD2 antagonist) and 2) that differential activation of genes may categorize clinical responders to this agent, critical for cost-effective use of this drug.

Homeostatic Tissue Responses in Skin Biopsies from NOMID Patients with Constitutive Overproduction of IL-1β

The autoinflammatory disorder, Neonatal-onset Multisystem Inflammatory Disease (NOMID) is the most severe phenotype of disorders caused by mutations in CIAS1 that result in increased production and secretion of active IL-1β. NOMID patients present with systemic and organ-specific inflammation of the skin, central nervous system and bone, and respond dramatically to treatment with IL-1 blocking agents. We compared the cellular infiltrates and transcriptome of skin biopsies from patients with NOMID (n = 14) before treatment (lesional (LS) and non-lesional (pre-NL) skin) and after treatment (post-NL) with the IL-1 blocker anakinra (recombinant IL-1 receptor antagonist, Kineret®, Swedish Orphan Biovitrum AB, SOBI), to normal skin (n = 5) to assess tissue responses in the context of untreated and treated disease. Abundant neutrophils distinguish LS skin from pre-NL and post-NL skin. CD11c+ dermal dendritic cells and CD163+ macrophages expressed activated caspase-1 and are a likely source of cutaneous IL-1 production. Treatment with anakinra led to the disappearance of neutrophils, but CD3+ T cells and HLA-DR+ cells remained elevated. Among the upregulated genes IL-6, IL-8, TNF, IL-17A, CCL20, and the neutrophil defensins DEFA1 and DEFA3 were differentially regulated in LS tissues (compared to normal skin). Important significantly downregulated pathways in LS skin included IL-1R/TLR signaling, type I and II cytokine receptor signaling, mitochondrial dysfunction, and antigen presentation. The differential expression and regulation of microRNAs and pathways involved in post-transcriptional modification were suggestive of epigenetic modification in the chronically inflamed tissue. Overall, the dysregulated genes and pathways suggest extensive “adaptive” mechanisms to control inflammation and maintain tissue homeostasis, likely triggered by chronic IL-1 release in the skin of patients with NOMID.