Asifa S. Haider

Psoriasis Vulgaris Lesions Contain Discrete Populations of Th1 and Th17 T Cells

The importance of T helper 17 (Th17) cells in inflammation and autoimmunity is now being appreciated. We analyzed psoriasis skin lesions and peripheral blood for the presence of IL-17-producing T cells. We localized Th17 cells predominantly to the dermis of psoriasis skin lesions, confirmed that IL-17 mRNA increased with disease activity, and demonstrated that IL-17 mRNA expression normalized with cyclosporine therapy. IL-22 mRNA expression mirrored IL-17 and both were downregulated in parallel with keratin 16. Th17 cells are a discrete population, separate from Th1 cells (which are also in psoriasis lesions), and Th2 cells. Our findings suggest that psoriasis is a mixed Th1 and Th17 inflammatory environment. Th17 cells may be proximal regulators of psoriatic skin inflammation, and warrant further attention as therapeutic targets.

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.

A Single Intradermal Injection of IFN-γ Induces an Inflammatory State in Both Non-Lesional Psoriatic and Healthy Skin

Psoriasis is a chronic, debilitating, immune-mediated inflammatory skin disease. As IFN-γ is involved in many cellular processes, including activation of dendritic cells (DCs), antigen processing and presentation, cell adhesion and trafficking, and cytokine and chemokine production, IFN-γ-producing Th1 cells were proposed to be integral to the pathogenesis of psoriasis. Recently, IFN-γ was shown to enhance IL-23 and IL-1 production by DCs and subsequently induce Th17 cells, important contributors to the inflammatory cascade in psoriasis lesions. To determine if IFN-γ indeed induces the pathways expressed in psoriasis lesions, a single intradermal injection of IFN-γ was administered to an area of clinically normal, non-lesional skin of psoriasis patients and biopsies were collected 24 hours later. Although there were no visible changes in the skin, IFN-γ induced many molecular and histological features characteristic of psoriasis lesions. IFN-γ increased a number of differentially expressed genes in the skin, including many chemokines concomitant with an influx of T cells and inflammatory DCs. Furthermore, inflammatory DC products TNF, iNOS, IL-23, and TRAIL were present in IFN-γ-treated skin. Thus, IFN-γ, which is significantly elevated in non-lesional skin compared to healthy skin, appears to be a key pathogenic cytokine that can induce many features of the inflammatory cascade of 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.