Fumi Miyagawa

The use of mouse models to better understand mechanisms of autoimmunity and tolerance

A major emphasis of our studies has been on developing a better understanding of how and why the skin serves as a target for immune reactions as well as how the skin evades becoming a target for destruction. For these studies we developed transgenic mice that express a membrane-tethered form of a model self antigen, chicken ovalbumin (mOVA), under the control of a keratin 14 (K14) promoter. K14-mOVA transgenic mice that express OVA mRNA and protein in the epithelia have been assessed for their immune responsiveness to OVA and are being used as targets for T cells obtained from OT-1 transgenic mice whose CD8+ T cells carry a Vα2/Vβ5-transgenic T cell receptor with specificity for the OVA(257-264)-peptides (OVAp) in association with class I MHC antigens. Some of the K14-mOVA transgenic mice develop a graft-versus-host-like disease (GvHD) when the OT-1 cells are injected while others appear to be tolerant to the OT-1 cells. We found that γc cytokines, especially IL-15, determine whether autoimmunity or tolerance ensues in K14-mOVA Tg mice. We also developed transgenic mice that express soluble OVA under the control of a K14 promoter (K14-sOVA) that die within 5-8 days after adoptive transfer of OT-1 cells and identified these mice as a model for more acute GvHD-like reactions. Spontaneous autoimmunity occurs when these K14-sOVA mice are crossed with the OT-I mice. In contrast, we found that preventive or therapeutic OVAp injections induced a dose-dependent increase in survival. In this review the characterization of 5 strains of K14-OVATg mice and underlying mechanisms involved in autoimmune reactions in these Tg mice are discussed. We also describe a strategy to break tolerance and describe how the autoimmunity can be obviated using OVAp. Finally, a historical overview of using transgenic mice to assess the mechanisms of tolerance is also provided.

Keratinocytes Function as Accessory Cells for Presentation of Endogenous Antigen Expressed in the Epidermis

The precise contribution(s) of skin dendritic cells (DCs) to immune responses in the skin has not been well delineated. We developed an intradermal (i.d.) injection model in which CD8+ T (OT-I) cells that express ovalbumin (OVA) peptide-specific TCRs (Valpha2/Vbeta5) are delivered directly to the dermis of transgenic (Tg) mice expressing OVA in the epidermis. After i.d. injection, these mice reliably develop skin graft-versus-host disease (GVHD) by day 7. To determine the relative contribution of Langerhans cells (LCs) to the ensuing GVHD-like reaction, we generated K14-OVA x Langerin-diphtheria-toxin-receptor (Langerin-DTR) Tg mice to allow conditional ablation of LCs in the epidermis. To delineate the role of dermal DCs (dDCs) in the reaction, we also generated K14-OVA Tg chimeras using beta(2)-microglobulin-deficient (beta(2)m) congenic donor bone marrow cells. Dermal DCs in these mice cannot present OVA to autoreactive T cells (OT-I cells), whereas the LCs are antigen presentation-competent. Unexpectedly, OT-I cell injection into diphtheria toxin (DT)-treated beta(2)m --> K14-OVA x Langerin-DTR Tg mice resulted in skin GVHD. Thus, in vivo, both LC and dDC appear to be dispensable for the induction of keratinocyte-directed, CD8-mediated effector immune responses. Furthermore and surprisingly, OVA-expressing epidermal cells depleted of LCs that could not initiate allogeneic epidermal lymphocyte reactions activated naive OT-I cells in vitro. These results indicate that keratinocytes may function as accessory cells competent to prime naive skin-reactive T cells.JID JOURNAL CLUB ARTICLE: For questions, answers, and open discussion about this article, please go to http://network.nature.com/group/jidclub.

Identification of thymus and activation-regulated chemokine (TARC/CCL17) as a potential marker for early indication of disease and prediction of disease activity in drug-induced hypersensitivity syndrome (DIHS)/drug rash with eosinophilia and systemic symptoms (DRESS).

BACKGROUND Drug-induced hypersensitivity syndrome (DIHS)/drug rash with eosinophilia and systemic symptoms (DRESS) is a serious acute drug reaction with fever, cutaneous eruption, lymphadenopathy, and several visceral dysfunctions. Eosinophilia is a common hematological abnormality in DIHS/DRESS suggesting that the Th2-type immune response is involved. Thymus and activation-regulated chemokine (TARC/CCL17) is a family of CC chemokines known to play an important role in Th2-mediated immune-inflammatory processes. OBJECTIVE We investigated the pathogenic role of TARC in patients with DIHS. METHODS Sera were obtained from 8 patients with DIHS, 7 patients with Stevens-Johnson syndrome/Toxic epidermal necrolysis (SJS/TEN), and 14 patients with drug-induced maculopapular exanthema (MPE). Serum TARC levels were measured by ELISA. TARC levels were then compared with clinical symptoms and various hematological parameters. In addition, a biopsy was taken from the lesional skin of patients with DIHS and stained with anti-TARC Ab and anti-CD11c Ab. RESULTS Serum TARC levels in patients with DIHS were significantly higher than those in patients with SJS/TEN and MPE during the acute phase. Serum TARC levels in DIHS patients correlated with skin eruptions, serum sIL-2R levels, eosinophil counts, and serum IL-5 levels. Immunohistochemical staining revealed that TARC was mainly expressed on CD11c+ dermal dendritic cells in patients with DIHS. CONCLUSION Serum TARC levels may be associated with the initial presentation of DIHS as well as disease activity during the course. Thus, they could be useful as an indicator for early diagnosis and assessment of disease activity in DIHS. CD11c+ dendritic cells may be the main source of TARC in patients with DIHS.

Efficacy of additional i.v. immunoglobulin to steroid therapy in Stevens-Johnson syndrome and toxic epidermal necrolysis.

Stevens–Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) are rare and life‐threatening cutaneous adverse drug reactions. While there is no established therapy for SJS/TEN, systemic corticosteroids, plasma exchange and i.v. immunoglobulin (IVIG) have been used as treatment. The efficacy of IVIG is still controversial because total doses of IVIG used vary greatly from one study to another. The aim of this study was to evaluate the efficacy of IVIG, administrated for 5 days consecutively, in an open‐label, multicenter, single‐arm study in patients with SJS or TEN. IVIG (400 mg/kg per day) administrated for 5 days consecutively was performed as an additional therapy to systemic steroids in adult patients with SJS or TEN. Efficacy on day 7 of IVIG was evaluated. Parameters to assess clinical outcome were enanthema including ophthalmic and oral lesions, cutaneous lesions and general condition. These parameters were scored and recorded before and after IVIG. We enrolled five patients with SJS and three patients with TEN who did not respond sufficiently to systemic steroids before IVIG administration. All of the patients survived and the efficacy on day 7 of the IVIG was 87.5% (7/8 patients). Prompt amelioration was observed in skin lesions and enanthema in the patients in whom IVIG therapy was effective. Serious side‐effects from the use of IVIG were not observed. IVIG (400 mg/kg per day) administrated for 5 days consecutively seems to be effective in patients with SJS or TEN. IVIG administrated together with steroids should be considered as a treatment modality for patients with refractory SJS/TEN. Further studies are needed to define the therapeutic efficacy of IVIG.

Interferon regulatory factor 8 integrates T-cell receptor and cytokine-signaling pathways and drives effector differentiation of CD8 T cells

We recently demonstrated that differentiation of cytotoxic T cells requires cooperation between T-cell receptor (TCR)/costimulation and γc-cytokines. Here we demonstrate that the transcription factor IFN regulatory factor 8 (IRF8) is expressed in CD8 T cells by the combination of these two signals. More importantly, depletion of IRF8 in these cells abrogated the differentiation of naive CD8 T cells into effector cells in an experimental graft-vs.-host disease mouse model. We also show that IRF8 seems to not operate upstream of other critical factors such as T-bet and eomesodermin, which have been implicated in effector maturation. Collectively, our work shows that IRF8 integrates the TCR/costimulation and γc-cytokine–signaling pathways and mediates the transition of naive CD8 T cells to effector cells, thus identifying IRF8 as one of the molecular regulators of CD8 T-cell differentiation.

IL-15 Serves as a Costimulator in Determining the Activity of Autoreactive CD8 T Cells in an Experimental Mouse Model of Graft-versus-Host-Like Disease

To elucidate the mechanisms controlling peripheral tolerance, we established two transgenic (Tg) mouse strains expressing different levels of membrane-bound OVA (mOVA) as a skin-associated self-Ag. When we transferred autoreactive TCR-Tg CD8 T cells (OT-I cells), keratin 14 (K14)-mOVAhigh Tg mice developed autoreactive skin disease (graft-vs-host disease (GVHD)-like skin lesions) while K14-mOVAlow Tg mice did not. OT-I cells in K14-mOVAhigh Tg mice were fully activated with full development of effector function. In contrast, OT-I cells in K14-mOVAlow Tg mice proliferated but did not gain effector function. Exogenous IL-15 altered the functional status of OT-I cells and concomitantly induced disease in K14-mOVAlow Tg mice. Conversely, neutralization of endogenous IL-15 activity in K14-mOVAhigh Tg mice attenuated GVHD-like skin lesions induced by OT-I cell transfer. Futhermore, K14-mOVAhigh Tg mice on IL-15 knockout or IL-15Rα knockout backgrounds did not develop skin lesions after adoptive transfer of OT-I cells. These results identify IL-15 as an indispensable costimulator that can determine the functional fate of autoreactive CD8 T cells and whether immunity or tolerance ensues, and they suggest that inhibition of IL-15 function may be efficacious in blocking expression of autoimmunity where a breach in peripheral tolerance is suspected.

Elevated serum thymus and activation‐regulated chemokine (TARC/CCL17) relates to reactivation of human herpesvirus 6 in drug reaction with eosinophilia and systemic symptoms (DRESS)/drug‐induced hypersensitivity syndrome (DIHS)

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Self-Peptides Prolong Survival in Murine Autoimmunity via Reduced IL-2/IL-7-Mediated STAT5 Signaling, CD8 Coreceptor, and Vα2 Down-Regulation

Although the pathogenic role of B cells and CD4 T cells has been studied extensively, less is known about the role of CD8 T cells in autoimmunity and self-tolerance. To evaluate the role of CD8 T cells in autoimmunity and its modulation using self-peptides, we used mice expressing soluble OVA (sOVA) under control of the keratin-14 promoter. Spontaneous autoimmunity occurred when sOVA mice were crossed with OT-I mice, whose CD8 T cells carry a Vα2/Vβ5-transgenic TCR with specificity for the OVA257–264 peptide. Eighty-three percent of OVA/OT-I mice died during the first 2 wk of life due to multiple organ inflammation. In contrast, preventive or therapeutic OVA257–264 peptide injections induced a dose-dependent increase in survival. Healthy survivors exhibited reductions in peripheral CD8 T cells, CD8 coreceptor, and Vα2 expression. Furthermore, CD8 T cells from healthy mice were anergic and could not be activated by exogenous IL-2. A block in IL-2/IL-7 signaling via the STAT5 pathway provided the basis for low surface expression of the CD8 coreceptor and failure of IL-2 to break CD8 T cell anergy. Thus, the soluble TCR ligand triggered multiple tolerance mechanisms in these sOVA/OT-I mice, making this treatment approach a potential paradigm for modulating human autoimmune diseases.

Identification of CD3+CD4−CD8− T Cells as Potential Regulatory Cells in an Experimental Murine Model of Graft-Versus-Host Skin Disease (GVHD)

We have developed K14-mOVA transgenic (Tg) mice that express membrane-associated ovalbumin (mOVA) under the control of a K14 promoter as well as double Tg mice by crossing them with OT-I mice that have a T cell receptor (TCR) recognizing OVA peptide. When injected with CD8+ OT-I cells, K14-mOVATg mice develop graft-vs-host disease (GvHD), whereas double Tg mice are protected. This suggests that, in double Tg mice, regulatory mechanisms may prevent infused OT-I cells from inducing GvHD. We demonstrated that, after adoptive transfer, TCRαβ+CD3+CD4-CD8-NK1.1- double negative (DN) T cells are increased in the peripheral lymphoid organs and skin of double Tg mice and exhibit a Vα2+Vβ5+TCR that is the same TCR specificity as OT-I cells. These DN T cells isolated from tolerant double Tg mice proliferated in response to OVA peptide and produced IFN-γ in the presence of IL-2. These cells could also suppress the proliferation of OT-I cells and were able to specifically kill activated OT-I cells through Fas/Fas ligand interaction. These findings suggest that DN T cells that accumulate in double Tg mice have regulatory functions and may play a role in the maintenance of peripheral tolerance in vivo.

Involvement of Human Herpesvirus 6 Infection in Renal Dysfunction Associated with DIHS/DRESS

Drug-induced hypersensitivity syndrome/drug reaction with eosinophilia and systemic symptoms (DIHS/ DRESS) is a life-threatening multi-organ hypersensitivity reaction that appears after prolonged exposure to a limited number of drugs. DIHS/DRESS is often related to reactivation of human herpesvirus 6 (HHV-6) (1–3). Renal dysfunction sometimes affects the prognosis (4). However, the pathomechanism of DIHS/DRESS-related renal dysfunction remains unknown. We report here a patient with DIHS/DRESS in whom HHV-6 infection may have been involved in the pathogenesis of renal failure.