Preferential expression of alphaEbeta7 integrin (CD103) on CD8+ T cells in the psoriatic epidermis: regulation by interleukins 4 and 12 and transforming growth factor-beta

Gut-tropic T cells and extra-intestinal autoimmune diseases

Gut-tropic T cells primarily originate from gut-associated lymphoid tissue (GALT), and gut-tropic integrins mediate the trafficking of the T cells to the gastrointestinal tract, where their interplay with local hormones dictates the residence of the immune cells in both normal and compromised gastrointestinal tissues. Targeting gut-tropic integrins is an effective therapy for inflammatory bowel disease (IBD). Gut-tropic T cells are further capable of entering the peripheral circulatory system and relocating to multiple organs. There is mounting evidence indicating a correlation between gut-tropic T cells and extra-intestinal autoimmune disorders. This review aims to systematically discuss the origin, migration, and residence of gut-tropic T cells and their association with extra-intestinal autoimmune-related diseases. These discoveries are expected to offer new understandings into the development of a range of autoimmune disorders, as well as innovative approaches for preventing and treating the diseases.

The biological basis of disease recurrence in psoriasis

Despite the amazing advances produced in our understanding of the pathogenesis of psoriasis, which have led to a therapeutic revolution, our knowledge of the mechanisms of relapse and elicitation of lesions is just starting to unravel. This narrative review tours the different cell types and mechanisms involved in the priming, maintenance, and relapse of psoriasis vulgaris. Our discussion includes dendritic cells, T cells, tissue resident memory cells and mast cells, with a foray into the epigenetic mechanisms of inflammatory memory in keratinocytes. Increasing knowledge is providing a glimpse of a potential therapeutic window of opportunity in psoriasis, providing long term remission and eventual modification of the natural history of the disease.

SMAD4 and TGFβ are architects of inverse genetic programs during fate-determination of antiviral CTLs

Transforming growth factor β (TGFβ) is an important differentiation factor for cytotoxic T lymphocytes (CTLs) and alters the expression levels of several of homing receptors during infection. SMAD4 is part of the canonical signaling network used by members of the transforming growth factor family. For this study, genetically modified mice were used to determine how SMAD4 and TGFβ receptor II (TGFβRII) participate in transcriptional programming of pathogen-specific CTLs. We show that these molecules are essential components of opposing signaling mechanisms, and cooperatively regulate a collection of genes that determine whether specialized populations of pathogen-specific CTLs circulate around the body, or settle in peripheral tissues. TGFβ uses a canonical SMAD-dependent signaling pathway to downregulate Eomesodermin (EOMES), KLRG1, and CD62L, while CD103 is induced. Conversely, in vivo and in vitro data show that EOMES, KLRG1, CX₃CR1, and CD62L are positively regulated via SMAD4, while CD103 and Hobit are downregulated. Intravascular staining also shows that signaling via SMAD4 promotes formation of long-lived terminally differentiated CTLs that localize in the vasculature. Our data show that inflammatory molecules play a key role in lineage determination of pathogen-specific CTLs, and use SMAD-dependent signaling to alter the expression levels of multiple homing receptors and transcription factors with known functions during memory formation.

Tissue-resident memory T cells and their biological characteristics in the recurrence of inflammatory skin disorders

The skin is the largest organ of the body. The establishment of immunological memory in the skin is a crucial component of the adaptive immune response. Once naive T cells are activated by antigen-presenting cells, a small fraction of them differentiate into precursor memory T cells. These precursor cells ultimately develop into several subsets of memory T cells, including central memory T (T_CM) cells, effector memory T (T_EM) cells, and tissue resident memory T (T_RM) cells. T_RM cells have a unique transcriptional profile, and their most striking characteristics are their long-term survival (longevity) and low migration in peripheral tissues, including the skin. Under physiological conditions, T_RM cells that reside in the skin can respond rapidly to pathogenic challenges. However, there is emerging evidence to support the vital role of T_RM cells in the recurrence of chronic inflammatory skin disorders, including psoriasis, vitiligo, and fixed drug eruption, under pathological or uncontrolled conditions. Clarifying and characterizing the mechanisms that are involved in skin T_RM cells will help provide promising strategies for reducing the frequency and magnitude of skin inflammation recurrence. Here, we discuss recent insights into the generation, homing, retention, and survival of T_RM cells and share our perspectives on the biological characteristics of T_RM cells in the recurrence of inflammatory skin disorders.

Resident-Memory T Cells in Tissue-Restricted Immune Responses: For Better or Worse?

Tissue-resident-memory CD8+ T cells (T_RM) have been described as a non-circulating memory T cell subset that persists at sites of previous infection. While T_RM in all non-lymphoid organs probably share a core signature differentiation pathway, certain aspects of their maintenance and effector functions may vary. It is well-established that T_RM provide long-lived protective immunity through immediate effector function and accelerated recruitment of circulating immune cells. Besides immune defense against pathogens, other immunological roles of T_RM are less well-studied. Likewise, evidence of a putative detrimental role of T_RM for inflammatory diseases is only beginning to emerge. In this review, we discuss the protective and harmful role of T_RM in organ-specific immunity and immunopathology as well as prospective implications for immunomodulatory therapy.

Review article: nonclinical and clinical pharmacology, pharmacokinetics and pharmacodynamics of etrolizumab, an anti-β7 integrin therapy for inflammatory bowel disease

BACKGROUND

Novel treatments with superior benefit-risk profiles are needed to improve the long-term prognosis of patients with inflammatory bowel disease (IBD). Etrolizumab-a monoclonal antibody that specifically targets β7 integrins-is currently under phase III clinical evaluation in IBD.

AIM

This review summarises the available pharmacological and pharmacokinetic/pharmacodynamic data for etrolizumab to provide a comprehensive understanding of its mechanism of action (MOA) and pharmacological effects.

METHODS

Published and internal unpublished data from nonclinical and clinical studies with etrolizumab are reviewed.

RESULTS

Etrolizumab exerts its effect via a unique dual MOA that inhibits both leucocyte trafficking to the intestinal mucosa and retention within the intestinal epithelial layer. The gut-selectivity of etrolizumab results from its specific targeting of the β7 subunit of α4β7 and αEβ7 integrins. Etrolizumab does not bind to α4β1 integrin, which mediates lymphocyte trafficking to tissues including the central nervous system, a characteristic underlying its favourable safety with regard to progressive multifocal leucoencephalopathy. Phase I/II studies in patients with ulcerative colitis (UC) showed linear pharmacokinetics when etrolizumab was administered subcutaneously at 100 mg or higher once every 4 weeks. This dose was sufficient to enable full β7 receptor occupancy in both blood and intestinal tissues of patients with moderate to severe UC. The phase II study results also suggested that patients with elevated intestinal expression of αE integrin may have an increased likelihood of clinical remission in response to etrolizumab treatment.

CONCLUSION

Etrolizumab is a gut-selective, anti-β7 integrin monoclonal antibody that may have therapeutic potential for the treatment of IBD.

A Yin and Yang in Epithelial Immunology: The Roles of the αE(CD103)β7 Integrin in T Cells

The proper function(s) of cell-surface receptors is crucial for the regulation of adaptive immune responses. One such receptor is the α_E(CD103)β₇ integrin, whose history in science is closely linked with the evolution of our knowledge of immune regulation. Initially described as a marker of intraepithelial T-lymphocytes, this leukocyte integrin is now seen as a dynamically regulated receptor involved in the functional differentiation of some cytotoxic T cells as well as regulatory T cells, thus presumably contributing to the fine-tuning of immune reactions in epithelial compartments. In this brief overview, we delineate our current view on α_E(CD103)β₇ in T-cell-mediated immune responses.

Integrin αEβ7: molecular features and functional significance in the immune system

Alpha E beta 7 (αEβ7) is an α-I domain-containing integrin that is highly expressed by a variety of leukocyte populations at mucosal sites including intraepithelial T cells, dendritic cells, mast cells, and T regulatory cells (Treg). Expression depends largely or solely on transforming growth factor beta (TGF-β) isoforms. The best characterized ligand for αEβ7 is E-cadherin on epithelial cells, though there is evidence of a second ligand in the human system. An exposed acidic residue on the distal aspect of E-cadherin domain 1 interacts with the MIDAS site in the αE α-I domain. By binding to E-cadherin, αEβ7 contributes to mucosal specific retention of leukocytes within epithelia. Studies on αE knockout mice have identified an additional important function for this integrin in allograft rejection and have also indicated that it may have a role in immunoregulation. Recent studies point to a multifaceted role for αEβ7 in regulating both innate and acquired immune responses to foreign antigen.

Essential role for CD103+ cells in the pathogenesis of spondyloarthritides

The clinical features of spondyloarthritides include extraarticular manifestations involving the skin, eyes, and gastrointestinal tract. At these sites, a membrane integrin can be acquired by virtue of the presence of CD4+ T cells and specific dendritic cells and correlates with a regulatory behavior of these cells. This membrane integrin conjugates the beta7 subunit and the alphaE subunit, also known as CD103. CD103 expression requires high levels of TGF-beta and retinoic acid; in addition, expression of CD103 by T cells requires antigen recognition. Whether CD103 is found in the entheses has not yet been investigated. CD103 is expressed at high levels in the skin, eyes, and bowel but it is found in only very low levels in the bloodstream. CD8+ CD103+ T cells differ markedly from other CD103+ cells in that they are resident cells with no tendency to migrate and usually exert predominantly cytotoxic functions as opposed to regulatory functions. Several bacteria, such as Salmonella, can become dormant within the mucous membranes and/or their lymph nodes, where they use CD103+ dendritic cells and CD4+ CD103+ regulatory T cells (Tregs) to evade the immune response. This phenomenon could be studied in other tissues targeted by spondyloarthritides, where dormant microorganisms can migrate by using M2 macrophages as Trojan horses, since M2 macrophages express the CD103 ligand E-cadherin. Microorganism peptide recognition by CD8+ CD103+ T cells (which are overrepresented in psoriasis and joint fluid in some forms of spondyloarthritis) induces an inflammatory response that may be sufficient to transiently reverse the regulatory function of the CD103+ dendritic cells and CD4+ CD103+ T cells during disease flares. The sensitivity of these diseases to retinoids further supports a pathogenic role for transient CD103+ cell failure.

Systemic sensitization with the protein allergen ovalbumin augments local sensitization in atopic dermatitis

Mouse models of atopic dermatitis based on epicutaneous sensitization have shed light on the role of epicutaneous allergen entry in the development of respiratory and gastrointestinal allergy. However, the contribution of non-cutaneous modes of sensitization to skin diseases has not been evaluated. We assessed if systemic ovalbumin administration, in conjunction with local sensitization, could prime for a robust inflammatory response. Furthermore, we attempted to elucidate important aspects of disease pathogenesis previously unaddressed in mouse models. Mice that underwent intraperitoneal ovalbumin sensitization prior to epicutaneous challenge demonstrated an acute (Th2-polarized) atopic dermatitis-like phenotype upon local challenge. The inflammatory response was strikingly more robust than in mice that underwent epicutaneous sensitization alone. The lesional infiltrate contained a dendritic cell population that corresponded phenotypically with inflammatory dendritic epidermal cells of significance in human disease. Finally, in accordance with observations in human atopic dermatitis, there was an increase in cluster of differentiation (CD) 103 (α_E subunit)-expressing CD4⁺ T lymphocytes. However, the absence of CD103 on approximately 50% of infiltrating cells argues against a primary role for the α_Eβ₇ integrin in tissue homing. In conclusion, we present a mouse model of atopic dermatitis that reveals novel insights into the pathogenesis of this complex disease.

The role of Th17/Tc17 peripheral blood T cells in psoriasis and their positive therapeutic response

It is known that NB-UVB therapy can suppress a broad range of immune cells, but the additional effect of bathing in geothermal seawater still remains unclear. To study the influence of treatment on the expression of circulating immune cells contributing to the pathogenesis of psoriasis, six patients with psoriasis were treated with bathing in geothermal seawater two times daily combined with NB-UVB five times/week for 2 weeks and six patients were treated with NB-UVB therapy three times/week for 8 weeks. Disease severity (Psoriasis Area and Severity Index, PASI), chemokines, inflammatory cytokines, T cells and Toll-like receptors in the blood and skin samples were evaluated on enrolment (W0) and at 1 (W1), 3 (W3) and 8 (W8) weeks. Compared with healthy controls, psoriasis patients with active disease had significantly higher proportion of peripheral CLA+ T cells expressing CCR10 and CD103 and T cells with both Th1/Tc1 (CD4+/CD8+ IFN-γ+ or TNF-α+ cells) and Th17/Tc17 (CD4+CD45R0+IL-23R+, CD4+/CD8+ IL-17A+ or IL-22+ cells) phenotypes. Both treatments gave a significant clinical effect; however, bathing in geothermal seawater combined with NB-UVB therapy was more effective than NB-UVB therapy alone. This clinical improvement was reflected by a reduction in circulating CLA+ peripheral blood T cells and by a decreased Th1/Th17 and Tc1/Tc17 inflammatory response. These findings suggest that the inflammatory response in psoriasis is predominantly driven by both CD4+ and CD8+ skin-homing tissue retaining T cells of the Th17/Tc17 lineages.

Local immunity by tissue-resident CD8(+) memory T cells

Microbial infection primes a CD8⁺ cytotoxic T cell response that gives rise to a long-lived population of circulating memory cells able to provide protection against systemic reinfection. Despite this, effective CD8⁺ T cell surveillance of barrier tissues such as skin and mucosa typically wanes with time, resulting in limited T cell-mediated protection in these peripheral tissues. However, recent evidence suggests that a specialized subset of CD103⁺ memory T cells can permanently lodge and persist in peripheral tissues, and that these cells can compensate for the loss of peripheral immune surveillance by circulating memory T cells. Here, we review evolving concepts regarding the generation and long-term persistence of these tissue-resident memory T cells (T_RM) in epithelial and neuronal tissues. We further discuss the role of T_RM cells in local infection control and their contribution to localized immune phenomena, in both mice and humans.

A humanized monoclonal antibody targeting the β7 integrin selectively blocks intestinal homing of T lymphocytes

BACKGROUND AND PURPOSE

rhuMAb Beta7 is a humanized anti-human β7 monoclonal antibody currently in phase I in inflammatory bowel disease. rhuMAb Beta7 binds the β7 subunit of the integrins α4β7 and αEβ7, blocking interaction with their ligands. These integrins play key roles in immune cell homing to and retention in mucosal sites, and are associated with chronic inflammatory diseases of the gastrointestinal tract. The goal of this study was to evaluate the mucosal specificity of rhuMAb Beta7.

EXPERIMENTAL APPROACH

We assessed the effect of murine anti-Beta7 on lymphocyte homing in mouse models of autoimmune disease. We also compared the effect of rhuMAb Beta7 on circulating mucosal-homing versus peripheral-homing T cells in naïve non-human primates.

KEY RESULTS

In cynomolgus monkeys, occupancy of β7 integrin receptors by rhuMAb Beta7 correlated with an increase in circulating β7(+) mucosal-homing lymphocytes, with no apparent effect on levels of circulating β7(-) peripheral-homing lymphocytes. rhuMAb Beta7 also inhibited lymphocyte homing to the inflamed colons of severe combined immunodeficient mice in CD45RB(high) CD4(+) T-cell transfer models. Consistent with a lack of effect on peripheral homing, in a mouse model of experimental autoimmune encephalomyelitis, anti-β7 treatment resulted in no amelioration of CNS inflammation.

CONCLUSIONS AND IMPLICATIONS

The results presented here suggest that rhuMAb Beta7 selectively blocks lymphocyte homing to the gastrointestinal tract without affecting lymphocyte trafficking to non-mucosal tissues. rhuMAb Beta7 provides a targeted therapeutic approach with the potential for a more attractive benefit:risk ratio than currently available inflammatory bowel disease therapies.

Evaluation of CD103 (αEβ7) integrin expression by CD8 T cells in blood as a surrogate marker to predict cervical T cell responses in the female genital tract during HIV infection

Mucosal homing receptors expressed by blood T cells may be useful surrogates for measuring mucosal T cell immune responses at the site of HIV transmission. Here, we investigated whether HIV-specific responses by T cells expressing the mucosal integrin receptor CD103 in blood reliably predicted corresponding HIV-specific responses at the cervix. The frequency of CD8+ T cells expressing CD103 in blood correlated significantly with the number of CD103+CD8+ T cells from the cervix suggesting that CD103 was involved in trafficking of T cells from blood to the cervical mucosa. TGF-β concentrations in plasma were significantly associated with the frequency of CD103 expression by blood but not cervical CD8 T cells. The majority of Gag-responsive CD8 T cells were CD103+ in both blood and at the cervix. Despite this, the magnitude of Gag-specific IFN-γ responses by CD103+CD8+ T cells in blood did not predict similar Gag-specific responses at the cervix.

Alternatively activated macrophages engage in homotypic and heterotypic interactions through IL-4 and polyamine-induced E-cadherin/catenin complexes

Alternatively activated macrophages (AAMs), triggered by interleukin-4 (IL-4) and IL-13, play a modulating role during Th2 cytokine-driven pathologies, but their molecular armament remains poorly characterized. Here, we established E-cadherin (Cdh1) as a selective marker for IL-4/IL-13-exposed mouse and human macrophages, which is STAT6-dependently induced during polarized Th2 responses associated with Taenia crassiceps helminth infections or allergic airway inflammation. The IL-4-dependent, arginase-1/ornithine decarboxylase-mediated production of polyamines is important for maximal Cdh1 induction, unveiling a novel mechanism for IL-4-dependent gene transcription. At the macrophage surface, E-cadherin forms a functional complex with the catenins that accumulates at sites of cell contact. Macrophage-specific deletion of the Cdh1 gene illustrates the implication of E-cadherin in IL-4-driven macrophage fusion and heterotypic interactions with CD103(+) and KLRG1(+) T cells. This study identifies the E-cadherin/catenin complex as a discriminative, partly polyamine-regulated feature of IL-4/IL-13-exposed alternatively activated macrophages that contributes to homotypic and heterotypic cellular interactions.

Immunopathogenesis of psoriasis

Psoriasis is a chronic skin disease that affects about 1.5% of the Caucasian population and is characterized by typical macroscopic and microscopic skin alterations. Psoriatic lesions are sharply demarcated, red and slightly raised lesions with silver-whitish scales. The microscopic alterations of psoriatic plaques include an infiltration of immune cells in the dermis and epidermis, a dilatation and an increase in the number of blood vessels in the upper dermis, and a massively thickened epidermis with atypical keratinocyte differentiation. It is considered a fact that the immune system plays an important role in the pathogenesis of psoriasis. Since the early 1990s, it has been assumed that T1 cells play the dominant role in the initiation and maintenance of psoriasis. However, the profound success of anti-tumor necrosis factor-alpha therapy, when compared with T-cell depletion therapies, should provoke us to critically re-evaluate the current hypothesis for psoriasis pathogenesis. Recently made discoveries regarding other T-cell populations such as Th17 and regulatory T cells, dendritic cells, macrophages, the keratinocyte signal transduction and novel cytokines including interleukin (IL)-22, IL-23 and IL-20, let us postulate that the pathogenesis of psoriasis consists of distinct subsequent stages, in each of them different cell types playing a dominant role. Our model helps to explain the varied effectiveness of the currently tested immune modulating therapies and may enable the prediction of the success of future therapies.

Alpha1beta1 integrin is crucial for accumulation of epidermal T cells and the development of psoriasis

Psoriasis is a common T cell-mediated autoimmune inflammatory disease. We show that blocking the interaction of alpha1beta1 integrin (VLA-1) with collagen prevented accumulation of epidermal T cells and immunopathology of psoriasis. Alpha1beta1 integrin, a major collagen-binding surface receptor, was exclusively expressed by epidermal but not dermal T cells. Alpha1beta1-positive T cells showed characteristic surface markers of effector memory cells and contained high levels of interferon-gamma but not interleukin-4. Blockade of alpha1beta1 inhibited migration of T cells into the epidermis in a clinically relevant xenotransplantation model. This was paralleled by a complete inhibition of psoriasis development, comparable to that caused by tumor necrosis factor-alpha blockers. These results define a crucial role for alpha1beta1 in controlling the accumulation of epidermal type 1 polarized effector memory T cells in a common human immunopathology and provide the basis for new strategies in psoriasis treatment focusing on T cell-extracellular matrix interactions.

Antibodies to Complement Receptor 3 Treat Established Inflammation in Murine Models of Colitis and a Novel Model of Psoriasiform Dermatitis

Prior studies indicated the ability of Abs to complement receptor 3 (CR3, CD11b/CD18) to suppress the production of IL-12 from immune cells. Therefore, we tested the ability of an anti-CR3 Ab (clone M1/70) to treat established IL-12-dependent Th1-mediated inflammation in murine models. Systemic administration of anti-CR3 significantly ameliorated established intestinal inflammation following the intrarectal administration of trinitrobenzene sulfonic acid (TNBS-colitis), as well as colitis and skin inflammation in C57BL/10 RAG-2(-/-) mice reconstituted with CD4+CD45RBhigh T cells. The hyperproliferative skin inflammation in this novel murine model demonstrated many characteristics of human psoriasis, and was prevented by the adoptive transfer of CD45RBlow T cells. In vitro and in vivo studies suggest that anti-CR3 treatment may act, at least in part, by directly inhibiting IL-12 production by APCs. Administration of anti-CR3 may be a useful therapeutic approach to consider for the treatment of inflammatory bowel disease and psoriasis in humans.

CD103 is a marker for alloantigen-induced regulatory CD8+ T cells

The alphaEbeta7 integrin CD103 may direct lymphocytes to its ligand E-cadherin. CD103 is expressed on T cells in lung and gut and on allograft-infiltrating T cells. Moreover, recent studies have documented expression of CD103 on CD4+ regulatory T cells. Approximately 4% of circulating CD8+ T cells bear the CD103 molecule. In this study, we show that the absence or presence of CD103 was a stable trait when purified CD103- and CD103+ CD8+ T cell subsets were stimulated with a combination of CD3 and CD28 mAbs. In contrast, allostimulation induced CD103 expression on approximately 25% of purified CD103- CD8+ T cells. Expression of CD103 on alloreactive cells was found to be augmented by IL-4, IL-10, or TGF-beta and decreased by addition of IL-12 to MLCs. The alloantigen-induced CD103+ CD8+ T cell population appeared to be polyclonal and retained CD103 expression after restimulation. Markedly, in vitro-expanded CD103+ CD8+ T cells had low proliferative and cytotoxic capacity, yet produced considerable amounts of IL-10. Strikingly, they potently suppressed T cell proliferation in MLC via a cell-cell contact-dependent mechanism. Thus, human alloantigen-induced CD103+ CD8+ T cells possess functional features of regulatory T cells.

NK cells and gamma delta+ T cells are phenotypically and functionally defective due to preferential apoptosis in patients with atopic dermatitis

Innate immune cells mediate a first line of defense against pathogens and determine the nature of subsequent acquired immune responses, mainly by producing profound amounts of cytokines. Given these diverse tasks, it is predictable that defective NK and gammadelta(+) T cell responses could be the underlying mechanism for the immunological alterations observed in atopic dermatitis (AD). Indeed, the frequencies of circulating NK cells and gammadelta(+) T cells were profoundly reduced in AD patients. They also displayed a defective ability to sustain TNF-alpha and IFN-gamma, but not IL-4, production after in vitro stimulation, and the defect was restricted to innate immune cells. Surprisingly, on the depletion of CD14(+) monocytes, this selective impairment of TNF-alpha and IFN-gamma production was restored to levels comparable to that observed in controls. Release of IL-10 from monocytes was not a major mechanism of the NK and gammadelta(+) T cell dysfunction. Apoptosis as revealed by annexin V binding, was preferentially observed in NK and gammadelta(+) T cells from AD patients when stimulated in the presence of monocytes, and depletion of monocytes significantly protected these cells from apoptotic cell death. Preferential apoptosis of NK cells by activated monocytes in AD patients was cell-contact-dependent. These results indicate that, once NK and gammadelta(+) T cells in AD patients are in immediate contact with activated monocytes, these cells are specifically targeted for apoptosis, leading to the reduced type 1 cytokine production, thereby directing subsequent acquired immune responses toward a type-2 pattern and increasing susceptibility to infection.

Critical role of the fifth domain of E-cadherin for heterophilic adhesion with alpha E beta 7, but not for homophilic adhesion

The integrin alpha(E)beta(7) is expressed on intestinal intraepithelial T lymphocytes and CD8(+) T lymphocytes in inflammatory lesions near epithelial cells. Adhesion between alpha(E)beta(7)(+) T and epithelial cells is mediated by the adhesive interaction of alpha(E)beta(7) and E-cadherin; this interaction plays a key role in the damage of target epithelia. To explore the structure-function relationship of the heterophilic adhesive interaction between E-cadherin and alpha(E)beta(7), we performed cell aggregation assays using L cells transfected with an extracellular domain-deletion mutant of E-cadherin. In homophilic adhesion assays, L cells transfected with wild-type or a domain 5-deficient mutant formed aggregates, whereas transfectants with domain 1-, 2-, 3-, or 4-deficient mutants did not. These results indicate that not only domain 1, but domains 2, 3, and 4 are involved in homophilic adhesion. When alpha(E)beta(7)(+) K562 cells were incubated with L cells expressing the wild type, 23% of the resulting cell aggregates consisted of alpha(E)beta(7)(+) K562 cells. In contrast, the binding of alpha(E)beta(7)(+) K562 cells to L cells expressing a domain 5-deficient mutant was significantly decreased, with alpha(E)beta(7)(+) K562 cells accounting for only 4% of the cell aggregates, while homophilic adhesion was completely preserved. These results suggest that domain 5 is involved in heterophilic adhesion with alpha(E)beta(7), but not in homophilic adhesion, leading to the hypothesis that the fifth domain of E-cadherin may play a critical role in the regulation of heterophilic adhesion to alpha(E)beta(7) and may be a potential target for treatments altering the adhesion of alpha(E)beta(7)(+) T cells to epithelial cells in inflammatory epithelial diseases.

Homing receptor and chemokine receptor on intraepidermal T cells in psoriasis vulgaris

Intraepidermal T lymphocytes found in psoriatic skin lesions are involved in the development and maintenance of lesional pathology. It has become clear that differential expression of homing and chemokine receptors determines the specific migration of T cells to distinct tissues and microenvironments, including psoriasis lesions. The aim of the present study was to clarify expression of homing (CLA, VLA-4, and LFA-1) and chemokine (CCR4, CCR6, CCR7, and CXCR3) receptors on intraepidermal T cells in psoriatic lesions using flow cytometry. The vast majority of intraepidermal T cells in psoriatic lesions expressed CLA and LFA-1, whereas 58% of CD4+ and 85% of CD8+ T cells expressed VLA-4. The majority of CD4+ T cells and about half of the CD8+ T cells expressed CCR4 and CCR6, whereas less than one-third of CD4+ and CD8+ T cells expressed CXCR3 or CCR7. In patients with psoriasis the percentages of T cells expressing CLA, CCR4, and CCR6 were much higher in the epidermis of psoriatic plaques than in the peripheral blood. Thus, CLA, CCR4, and CCR6 may play a more important role in the migration of T cells to psoriatic epidermis.

Psoriasis vulgaris: an interplay of T lymphocytes, dendritic cells, and inflammatory cytokines in pathogenesis

PURPOSE OF REVIEW

Discuss and update concepts and hypotheses for the pathogenesis of psoriasis based on new research reports (primarily from 2003 and early 2004).

RECENT FINDINGS

Increases in newly defined dendritic cell subsets, cytokines, and chemokines have been identified in psoriasis lesions and have modified views of T-cell-mediated pathogenesis. In addition, the psoriasis transcriptome has been defined by large-scale genomic expression studies, and these data suggest distinct molecular mechanisms of type 1 T-cell-mediated inflammation. Somewhat surprisingly, therapeutic clinical trials suggest that tumor necrosis factor is a major pathogenic cytokine in psoriasis, whereas translational studies point to roles of other innate pathways mediated by heat shock proteins, glycolipids, natural killer T cells, or dendritic cells in disease pathogenesis.

SUMMARY

An interactive network of inflammatory cytokines, chemokines, dendritic cells, and type 1 T cells or natural killer T cells potentially drives pathogenic inflammation in psoriasis vulgaris. Continued clinical studies with defined immune antagonists provide a critical means to dissect the contribution of different cell subsets and genomic pathways to the pathogenesis of psoriasis vulgaris.

Murine CD8+Recent Thymic Emigrants are αEIntegrin-Positive and CC Chemokine Ligand 25 Responsive

Recent thymic emigrants (RTE) are an important subpopulation of naive CD8+ T cells because of their ability to reconstitute a diverse immune system after periods of T cell depletion. In neonatal mice, the majority of peripheral T lymphocytes are RTE, cells that have recently left the thymus to populate the periphery. Postulating that these cells could have unique trafficking mechanisms, we compared adhesion molecule and chemokine receptor expression of neonatal RTE with mature adult lymphocytes. Neonatal CD8+ splenocytes uniformly express alpha(E) integrin and exhibit a high responsiveness to CC chemokine ligand (CCL25) (as compared with adult CD8+ splenocytes). Mature CD8+ thymocytes have a similar alpha(E) integrin(+) CCL25 responsive phenotype, as do adult CD8+ RTE identified by intrathymic FITC injection. With increasing age, the frequency of CD8+ alpha(E) integrin(+) splenocytes decreases, roughly correlating with thymic involution. Moreover, halting thymic output by thymectomy accelerates the age-dependent decline in peripheral CD8+ alpha(E) integrin(+) RTE phenotype cells. Low expression of CD44 distinguishes these CD8+ RTE from a population of memory phenotype alpha(E) integrin(+) CD8+ cells that are CD44(high). We conclude that CD8+ RTE have unique adhesive and chemotactic properties that distinguish them from naive CD8+ T cells. These properties may enable specialized microenvironmental and cell-cell interactions contributing to the fate of RTE in the periphery during the early post-thymic period. This phenotype will also facilitate the identification and isolation of RTE for further studies.

Differential effects of interleukin 12 and interleukin 10 on superantigen-induced expression of cutaneous lymphocyte-associated antigen (CLA) and αEβ7 integrin (CD103) by CD8+ T cells

At both cutaneous and mucosal sites, interleukin (IL)-10, IL-12 and transforming growth factor (TGF)-beta are important regulators of chronic inflammatory disease, where cutaneous lymphocyte-associated antigen (CLA) and alphaE integrin (CD103) may be expressed. Stimulation with streptococcal pyrogenic exotoxin C (SpeC) increased the expression of CD103 by CD8+ but not CD4+ T cells. While adding IL-12 augmented the expression of CLA, superantigen-induced expression of CD103 was markedly suppressed by IL-12, which could be reversed by TGF-beta. Antibodies against TGF-beta inhibited, and a combination of anti-TGF-beta and IL-12 completely abrogated the induced CD103 expression. IL-10 strongly decreased the frequency of CLA+ and although not increasing the frequency of CD103+CD8+ T cells, the amount of CD103 expressed per cell was markedly increased. Thus, the expression of CLA and CD103 may be antagonistically regulated by IL-10 and IL-12 and the balance between these cytokines could influence the T cell migration of inflammatory cells into epithelial tissues.