TSLP expression: analysis with a ZsGreen TSLP reporter mouse.

Thymic stromal lymphopoietin (TSLP) is a type I cytokine that plays a central role in induction of allergic inflammatory responses. Its principal targets have been reported to be dendritic cells and/or CD4 T cells; epithelial cells are a principal source. We report in this study the development of a reporter mouse (TSLP-ZsG) in which a ZsGreen (ZsG)-encoding construct has been inserted by recombineering into a bacterial artificial chromosome immediately at the translation initiating ATG of TSLP. The expression of ZsG by mice transgenic for the recombinant BAC appears to be a faithful surrogate for TSLP expression, particularly in keratinocytes and medullary thymic epithelial cells. Limited ZsG and TSLP mRNA was observed in bone marrow-derived mast cells, basophils, and dendritic cells. Using the TSLP-ZsG reporter mouse, we show that TNF-α and IL-4/IL-13 are potent inducers of TSLP expression by keratinocytes and that local activation of Th2 and Th1 cells induces keratinocyte TSLP expression. We suggest that the capacity of TSLP to both induce Th2 differentiation and to be induced by activated Th2 cells raises the possibility that TSLP may be involved in a positive feedback loop to enhance allergic inflammatory conditions.

CXCR3-mediated skin homing of autoreactive CD8 T cells is a key determinant in murine graft-versus-host disease.

The pathomechanisms underlying the development of cutaneous graft-versus-host disease (GVHD) are incompletely defined. We previously reported that K14-mOVA mice expressing membrane ovalbumin (mOVA), driven by the keratin 14 (K14) promoter, developed GVHD-like mucocutaneous disease and weight loss following transfer of OVA-specific, CD8(+) OT-I T cells. In this study, we demonstrate that early in the course of disease, the kinetics of epidermal expression of C-X-C motif chemokine ligand 9 (CXCL9) and CXCL10, interferon-γ-inducible chemokines that bind the C-X-C motif chemokine receptor 3 (CXCR3) receptor, coincides with CXCR3 expression by OT-I cells in secondary lymphoid organs. Recruitment of OT-I cells into the skin began by day 5 with progressive accumulation through day 13 post transfer. Transfer of CXCR3-knockout (CXCR3KO) OT-I cells into K14-mOVA mice resulted in strikingly attenuated skin disease. CXCR3KO OT-I cells retained full activation and effector function, but preferentially accumulated in the spleen, in contrast to wild-type (WT) OT-I cells that accumulated in skin-draining lymph nodes. Moreover, OT-I cells accounted for a significantly reduced percentage of skin-infiltrating lymphocytes in mice receiving CXCR3KO OT-I cells compared with WT OT-I cells. These results identify CXCR3 as being critical to the skin-selective effector T-cell recruitment underlying autoreactive GVHD, suggesting CXCR3 as a potential target in the treatment of GVHD and related skin diseases.

Reversal of CD8 T-cell-mediated mucocutaneous graft-versus-host-like disease by the JAK inhibitor tofacitinib.

The utility of allogeneic hematopoietic stem cell transplantation is limited by graft-versus-host disease (GVHD), a significant cause of morbidity and mortality. Patients with GVHD exhibit cutaneous manifestations with histological features of interface dermatitis followed by scleroderma-like changes. JAK inhibitors represent a class of immunomodulatory drugs that inhibit signaling by multiple cytokines. Herein we report the effects of tofacitinib in a murine model of GVHD. Oral administration of tofacitinib prevented GVHD-like disease manifested by weight loss and mucocutaneous lesions. More importantly, tofacitinib was also effective in reversing established disease. Tofacitinib diminished the expansion and activation of murine CD8 T cells in this model, and had similar effects on IL-2-stimulated human CD8 T cells. Tofacitinib also inhibited the expression of IFN-γ-inducible chemoattractants by keratinocytes, and IFN-γ-inducible cell death of keratinocytes. Tofacitinib may be an effective drug for treatment against CD8 T-cell-mediated mucocutaneous diseases in patients with GVHD.

Soluble peptide treatment reverses CD8 T-cell-induced disease in a mouse model of spontaneous tissue-selective autoimmunity.

Transgenic (Tg) mouse models of autoimmunity have been used to express model antigens that can be recognized by T cells or by autoantibodies. To identify mechanisms of CD8-mediated tissue-specific autoimmune reactions and to identify potential treatments, we generated a double-transgenic (DTg) murine model of autoimmunity by crossing keratin-14 (K14)-soluble chicken ovalbumin (sOVA) mice, which express sOVA predominantly in external ear skin, with OT-I mice whose CD8 T cells express Vα2/Vß5 regions of the TCR and are specific for SIINFEKL peptide (chicken ovalbumin (OVA) peptide 257-264) in association with class I major histocompatibility complex. The K14-sOVA/OT-I DTg mice develop a destructive process selectively targeting the external ear pinnae in the first 6 days of life. The ear bud area develops an intense inflammatory infiltrate of OT-I cells. Administration of the SIINFEKL peptide intravenously to pregnant F1 (filial 1, first filial generation of animal offspring from cross-mating two parental types) mice and subsequently intraperitoneally to newborn pups resulted in normal external ear development. Treatment with this self-peptide markedly reduced OT-I cell numbers, as well as downregulated the CD8 co-receptor. This model can be useful in studying localized, tissue-specific, immune-mediated skin disease, and provide information about potential therapies for autoimmune diseases in which specific molecular targets are known.

Soluble proteins and haptens on bone marrow-derived dendritic cells are presented to host CD4 T cells in an MHC-restricted manner.

Because of their potent antigen-presenting capacity, dendritic cells (DC) have been used extensively in immunotherapy protocols. Our purpose was to functionally characterize mouse bone marrow-derived DC (BMDC) in vitro (in protein antigen- and hapten-specific assays) and in vivo (injecting soluble protein- and hapten-pulsed DC) to determine their suitability for the generation of T(h) cell responses. Furthermore, we determined whether there is cross-presentation on MHC class II molecules during in vivo protein and hapten sensitization. Co-culture of protein-pulsed [with hen egg lysozyme (HEL) or with pigeon cytochrome c (CYT)] DC with T cells from HEL- or CYT- sensitized mice induced antigen-specific T cell proliferation, but compared to cultured Langerhans cells (LC), BMDC required higher protein antigen-pulsing concentrations (100 microg and 1 mg/ml). In contrast, at low protein concentrations (10 microg/ml), BMDC stimulated an HEL-specific hybridoma very efficiently. Using an in vitro T cell proliferation assay and in vivo delayed-type hypersensitivity and contact sensitivity assays, we found that protein- and hapten-pulsed BMDC were able to sensitize syngeneic but not allogeneic hosts. Furthermore, if we injected BALB/c- and C57BL/6-derived HEL-pulsed BMDC into F1 mice, specific secondary proliferation of primed T cells occurred only when antigen-pulsed stimulator cells syngeneic to the injected BMDC were used. Using this model system we found that soluble proteins and haptens are presented by injected BMDC to host T cells in an MHC-restricted manner in vivo.