HOMOLOGOUS DISEASE IN THE ADULT RAT, A MODEL FOR AUTOIMMUNE DISEASE. I. GENERAL FEATURES AND CUTANEOUS LESIONS

Chronic GvHD NIH Consensus Project Biology Task Force: evolving path to personalized treatment of chronic GvHD

Chronic graft-versus-host disease (cGvHD) remains a prominent barrier to allogeneic hematopoietic stem cell transplantion as the leading cause of nonrelapse mortality and significant morbidity. Tremendous progress has been achieved in both the understanding of pathophysiology and the development of new therapies for cGvHD. Although our field has historically approached treatment from an empiric position, research performed at the bedside and bench has elucidated some of the complex pathophysiology of cGvHD. From the clinical perspective, there is significant variability of disease manifestations between individual patients, pointing to diverse biological underpinnings. Capitalizing on progress made to date, the field is now focused on establishing personalized approaches to treatment. The intent of this article is to concisely review recent knowledge gained and formulate a path toward patient-specific cGvHD therapy.

The Role of Animal Models in the Study of Hematopoietic Stem Cell Transplantation and GvHD: A Historical Overview

Bone marrow transplantation (BMT) is the only therapeutic option for many hematological malignancies, but its applicability is limited by life-threatening complications, such as graft-versus-host disease (GvHD). The last decades have seen great advances in the understanding of BMT and its related complications; in particular GvHD. Animal models are beneficial to study complex diseases, as they allow dissecting the contribution of single components in the development of the disease. Most of the current knowledge on the therapeutic mechanisms of BMT derives from studies in animal models. Parallel to BMT, the understanding of the pathophysiology of GvHD, as well as the development of new treatment regimens, has also been supported by studies in animal models. Pre-clinical experimentation is the basis for deep understanding and successful improvements of clinical applications. In this review, we retrace the history of BMT and GvHD by describing how the studies in animal models have paved the way to the many advances in the field. We also describe how animal models contributed to the understanding of GvHD pathophysiology and how they are fundamental for the discovery of new treatments.

Collagen deposition in autoimmune diseases: the expanding role of the fibroblast in human fibrotic disease

Fibrosis, usually considered an extension of the normal process of wound healing, follows to a variable degree host responses of an inflammatory nature, both immune and non-immune. The immediate mesenchymal effector cell of fibrosis, the fibroblast, has more or less been taken for granted in this process, due largely to its monotonous morphological uniformity. An emerging realization that the fibroblast can react in a variety of ways, both as an amplifying population of cells and in selective ways as the final arbiter of the extracellular matrix, is the subject of this report. This heterogeneity of fibroblast behaviour is characterized and, since many types of cells (endothelial, smooth muscle, epithelial) have now been shown to respond to matrix-derived signals, the potential for mesenchymal cell selection as a mechanism for understanding human fibrotic disease is probed. Signals which selectively alter fibroblast proliferation and fibroblast phenotypic expression are emphasized.

Scleroderma-like remodeling induced by type V collagen

Recently, we discovered that New Zealand rabbits immunized with human type V collagen plus Freund's adjuvant present fibrosis and vasculitis of organs usually affected by systemic sclerosis. In this way, we studied the fibrillogenesis process to identify possible factors involved in altered remodeling observed in this scleroderma-like model. Additionally, we have done a very preliminary comparison with human skins obtained from scleroderma patients (n=3). Female New Zealand rabbits (n=10) were immunized subcutaneously with two doses of 1 mg collagen V (COL V) plus complete Freund's adjuvant for a 30-day interval, followed by two additional intramuscular booster immunizations in incomplete Freund's adjuvant for a 15-day interval. Animals from control group (n=10), were only inoculated with complete and incomplete Freund's adjuvant given at same conditions of COL V. Histological analysis of skins from animals and patients were done by Masson's trichrome staining, and immunofluorescence method to detect collagen fibers and interactions of types I, III and V collagen in the remodeling process. The analysis of animal skins showed collagen fibril deposits in the dermis after 7 days of sensibilization and an increase in these deposits after 75 and 120 days, respectively. Skin thickness and atrophy of sebaceous and sweat glands were progressively more intense in late sacrificed animals and correlated with increased amount of collagen deposition. Surprisingly, type V collagen was overexpressed both in animals and patients, forming dense and atypical collagen fibers in the dermis. We suggest that this anomalous expression of morphologically different type V collagen could justify the remodeling observed in scleroderma plaque.

The Parent-into-F1 Model of Graft-vs-Host Disease as a Model of In Vivo T Cell Function and Immunomodulation

Since its description roughly 30 years ago, the parent-into-F1 model of graft-vs.-host disease has provided insights into the mechanisms of in vivo T cell activation and the pathogenesis of autoimmune conditions. A new and emerging role for the P-->F1 model is one of identifying agents with immunomodulatory activity and defining in vivo mechanisms that promote cell mediated or antibody mediated immune responses. Because F1 mice are not irradiated prior to donor cell transfer, the P-->F1 model has in the past not been strictly analogous to human hematopoetic stem cell transplantation. However with the advent of newer non-myeloablative conditioning regimens, the model may assume more relevance. In this article, we first provide a review of relevant earlier fundamental observations followed by a summary of recent work from our laboratory in which acute and chronic GVHD in this model have been used not only to study normal T cell responses in vivo but also to define mechanisms important in the pathogenesis of autoimmunity and immunomodulation.

A pediatric case of sclerodermatous chronic graft-versus-host disease

We report a rare case of sclerodermatous chronic graft-versus-host disease (GVHD) in a 6-year-old boy that occurred after bone marrow transplantation for his aplastic anemia. The clinical manifestation and histopathologic findings were typical of scleroderma. Although various kinds of treatment have been tried for scleroderma, no established therapy exists. Furthermore, treating this disease is even more difficult in children. In the future, clarification of the pathogenesis of chronic GVHD and establishment of therapy will be necessary.

Animal models for scleroderma: an update

Scleroderma is a progressive debilitating fibrosing disease that may involve multiple organs. The pathogenesis of this disease remains unclear. Animal models for scleroderma are valuable for studying the pathogenesis of this complex disorder and for testing potential treatments for human scleroderma. There are several animal models available that exhibit important features of scleroderma, each with an emphasis on different aspects of the disease (tissue fibrosis, inflammation, vascular injury, or immunologic changes). These models can be separated into several categories in which fibrosis is induced by external agents (vinyl chloride, bleomycin), by breeding of mutant strain combinations (integrin alpha 1 null mouse, MRL/lpr gamma R-/- mouse), and by transplantation of disparate immune cells (sclerodermatous graft versus host disease). In addition, there are spontaneous mutations (UCD 200 chicken, tight skin mouse) in which fibrosis occurs. The tight skin mouse has been reviewed recently. This review discusses the other animal models and some interventions in each.

Increased numbers of microchimeric cells of fetal origin are associated with dermal fibrosis in mice following injection of vinyl chloride

OBJECTIVE

To develop a murine model for use in examining the role of microchimeric cells and certain chemical exposures in the pathogenesis of systemic sclerosis (SSc).

METHODS

Female BALB/cJ retired breeder mice were bled before and after vinyl chloride injection. The DNA from their white blood cells was obtained, and the number of microchimeric cell equivalents was determined by quantitative polymerase chain reaction using DNA primers specific for the H-2Kb gene, a sequence not found in BALB/cJ mice. Skin was obtained at autopsy, embedded in paraffin, sectioned, and stained with Masson's trichrome. Hydroxyproline analyses were performed on 4-mm skin biopsy samples.

RESULTS

Microchimeric cells were identified and quantitated before and after 20 daily intraperitoneal injections of vinyl chloride. The number of microchimeric cells in the peripheral blood increased an average of 48-fold after treatment with vinyl chloride. Histologic examination of the skin of these same mice (which had an increased number of microchimeric cells) showed inflammation, with abundant fibroblasts and a heavy mononuclear infiltration in the dermis. The collagen fibers appeared densely packed and disorganized. Histologic examination of the skin of untreated retired breeder mice and treated virgin mice appeared normal. Quantitative assays to determine the collagen content of skin biopsy samples obtained from treated microchimeric mice compared with nontreated microchimeric or with treated nonmicrochimeric mice showed a 2-3-fold increase in collagen content in the treated microchimeric mice. Extraordinary splenomegaly was present in the vinyl chloride-treated microchimeric mice, accompanied by cellular infiltration and fibrosis.

CONCLUSION

The results suggest that vinyl chloride injections into BALB/cJ retired breeder mice lead to activation of microchimeric cells, which causes the cells to divide and multiply. The correlation between the 48-fold increase in microchimeric cells and the appearance of dermal inflammation and fibrosis similar to that of graft-versus-host disease suggests that activated microchimeric cells may be a necessary factor in the pathogenesis of autoimmune diseases such as SSc.

New perspectives on the etiology of systemic sclerosis

Systemic sclerosis (SSc) is a disease of unknown origin. Although SSc is considered to be an autoimmune disease, recent studies have implicated cellular microchimerism in its pathogenesis. Microchimerism results from the persistence of fetal cells, from prior pregnancies, in the maternal circulation. The demonstration of the presence of fetal CD3+ T cells in the maternal circulation and of fetal cells in affected SSc tissues suggests that microchimerism might cause SSc in certain patients by initiating a graft-versus-host-like response.

Role of T cells and cytokines in effecting fibrosis

A number of humoral and cellular immune abnormalities are present in patients with early scleroderma (systemic sclerosis). Most of these abnormalities reflect ongoing autoimmune reactions of the cellular and humoral types, resulting in a variety of autoantibodies to cellular and tissue constituents. Evidence exists for a defect(s) in immunoregulation favoring excessive helper T cell activity. The presence of circulating cytokines and shed interleukin-2 receptors suggest ongoing cellular immune reactions are occurring, generating cytokines and lymphokines that are capable of effecting the vascular and fibrotic lesions that are hallmarks of the disease. Future directions for research are suggested that would focus on determining if, and at what point, fibroblasts might function autonomously to generate excessive matrix components and on determining the nature of the original antigenic stimulus that starts the scleroderma process.

Autoantibodies in scleroderma and tightskin mice

There is much evidence to suggest that scleroderma in human patients is caused by a fundamental defect in the immune system. In tightskin mice, the scleroderma syndrome is associated with autoimmunity, particularly autoantibodies interacting with scleroderma target antigens.

Transfer of the inflammatory disease of HLA-B27 transgenic rats by bone marrow engraftment

We have previously produced lines of rats transgenic for HLA-B27 and human beta 2-microglobulin (h beta 2m) that develop a progressive inflammatory disease sharing many clinical and histologic features with the B27-associated human spondyloarthropathies, including gut and male genital inflammation, arthritis, and psoriasiform skin lesions. Other transgenic lines that express lower levels of B27 and h beta 2m remain healthy. To investigate the cellular basis for the multisystem inflammatory disease in these rats, we transferred lymphoid cell populations from disease-prone transgenic lines to irradiated disease-resistant transgenic and nontransgenic recipients. In recipients of cells from two different disease-prone lines, successful transfer required engraftment of bone marrow cells. Transfer of disease with fetal liver cells suggested that neither mature effector cells nor active disease in the donors was necessary for induction of disease in the recipients. Remission of the spontaneous disease in irradiated transgenic rats was induced by engraftment of nontransgenic bone marrow. These results suggest that the expression of HLA-B27 in bone marrow-derived cells alone is sufficient for the development of B27-associated disease, and that disease transfer requires engraftment of a bone marrow precursor cell for which mature cells in spleen or in lymph node cannot substitute.

Increased interleukin-2 production in response to human type I collagen stimulation in patients with systemic sclerosis

Peripheral blood mononuclear cells (PBMC) from patients with systemic sclerosis (SSc) produced increased amounts of interleukin-2 (IL-2), in a dose-dependent manner, in response to stimulation with human type I collagen, whereas PBMC from normal subjects did not. At a dose of 50 micrograms human type I collagen/10(6) PBMC, PBMC from SSc patients (n = 17) produced 8 times as much IL-2 as did PBMC from 16 normal subjects (P less than 0.005) and 3 times as much as did PBMC from a group of 13 rheumatoid arthritis patients (P less than 0.05). In contrast, IL-2 production by PBMC after nonspecific stimulation with the mitogen, phytohemagglutinin, did not differ among the SSc, rheumatoid arthritis, and normal control groups. Cell depletion experiments indicated that the IL-2-producing cells in SSc patients are CD4+. Thus, SSc patients have CD4 cells that are specifically sensitized to human type I collagen and can produce increased levels of IL-2. Measurement of IL-2 production stimulated by human type I collagen may be useful in evaluating disease activity, and further investigation of this process may contribute to the delineation of the pathogenesis of SSc.

Self reactive repertoire of tight skin mouse: immunochemical and molecular characterization of anti-topoisomerase I autoantibodies

Tight skin (TSK) mice develop cutaneous hyperplasia accompanied by histopathological alterations of skin and collagen metabolism similar to those described in human scleroderma. Diffuse scleroderma, the most severe form of progressive systemic sclerosis, is associated with the production of autoantibodies specific for Scleroderma 70 antigen (topoisomerase I). Our studies show that there is an increase in the level of serum anti-topoisomerase I (topo I) autoantibodies in aged TSK mice. The monoclonal antibodies isolated from TSK mice bind to epitopes which interact with autoantibodies from scleroderma patients. A significant number of TSK monoclonal anti-topo I antibodies and serum immunoglobulin (Ig) from aged TSK mice bear a cross reactive idiotype (Id) recognized by a syngeneic monoclonal anti-Id antibody obtained from a 2 month-old TSK mouse. Analysis of V gene usage by monoclonal anti-topo I antibodies showed that the majority of these antibodies are encoded by VH genes derived from VHJ558 family pairing with VK genes from various families in a stochastic manner.

Histamine release from mouse and rat mast cells cultured with supernatants from chronic murine graft-vs-host splenocytes

There is growing interest in studying pathways of mast cell activation. In a mouse model of chronic graft-vs-host disease (cGVHD) extensive mast cell activation and degranulation occurs in vivo coincident with the development of dermal fibrosis. An interesting feature of this model is that the mast cell reaction is slow to develop, occurring over a period of weeks and waning by 300 days. The aim of our work was to investigate the effects of supernatants from splenocytes of such cGVHD mice (cGVHD sups) on mouse and rat peritoneal mast cells cocultured with 3T3 skin fibroblasts. We found that cGVHD sups are able to release histamine from both mouse and rat cultured mast cells in a slow fashion. Histamine release became evident only after 5-8 days of coculture of the mast cells with the cGVHD supernatants and thereafter decreased to basal levels. Mast cell activation due to cGVHD supernatants was a noncytotoxic event as demonstrated by mast cell counts in the cocultures and by the ability of mast cells to exclude trypan blue. Mast cells that had been activated by incubation with the cGVHD sups were as responsive to stimulation with either anti-IgE antibodies or compound 48/80 as were mast cells incubated with control sups. Supernatants from mice early in GVHD (Days 11-28) were most active in promoting histamine release. Supernatants from spleens of mice which had GVHD for 290 days and where the mast cells had returned to full granulation in vivo were inactive. This is the first in vitro study demonstrating slow mast cell histamine release instituted by other cells, namely the splenocytes of cGVHD mice.

Chronic cyclosporine-induced autoimmune disease in the rat: a new experimental model for scleroderma

The pathogenesis of scleroderma is still elusive, although autoimmune mechanism involvement has been suggested. The present study was designed to investigate whether or not rat scleroderma would appear as one of the symptoms in a recently described model for autoimmune disease. The model is based on manipulation or reconstitution of the immune system after lethal irradiation and syngeneic bone marrow transplantation by temporary administration of the immunosuppressive drug cyclosporine-A. Withdrawal of cyclosporine-A 6-12 wk after bone marrow transplantation gives rise to autoimmune reactions causing clinical pathology similar to graft-versus-host disease. We discuss the chronic phase of this disease, approximately 30 wk after cyclosporine-A was withheld at that time-about one-third of the rats had developed histologic skin lesions comparable to those seen in patients with scleroderma. Therefore, we propose this model as a new, experimental autoimmune model for scleroderma in humans.

Graft-versus-host-related immunosuppression is induced in mixed chimeras by alloresponses against either host or donor lymphohematopoietic cells

Graft-vs.-host (GVH)-related immunosuppression has previously been demonstrated in F1 rodent recipients of parental lymphoid cells, and has been thought to result from an immunologic attack of the donor against the host. Since all cells of such F1 recipients could potentially bear target class I MHC alloantigens, it has not previously been possible to determine precisely the target tissues responsible for development of GVH-related effects. In the present studies we have used mixed allogeneic chimeras as recipients of host or donor-strain lymphocyte inocula, and have made the surprising observation that "GVH-induced" immune unresponsiveness does not require GVH reactivity, per se, but develops in the presence of a one-way alloresponse against lymphohematopoietic cells in either the GVH or the host-versus-graft direction.

Mechanism of anti-asialo GM1 prevention of graft-vs-host disease: identification of allo-antigen activated T cells

The purpose of this study was to begin to dissect the mechanism whereby anti-asialo GM1 (alpha ASGM1) prevents otherwise lethal graft-vs-host disease (GVHD) across multiple minor histocompatibility barriers in mice. Phenotypic characterization of cells from the peak proliferative time of the graft-vs-host reaction (C57BL/6J lymph node cells----irradiated LP/J, days 5-7) revealed the alpha ASGM1 and alpha Thy 1.2 identified cells with an approximate 80% concordance and that NK-1.1 staining was negligible. Because resting T cells do not label with alpha ASGM1, the epitope recognized by alpha ASGM1 on GVHR T cells is an activation antigen. Because asialo GM1 has been previously found on the surface of activated macrophages, we wanted to distinguish between the two most likely targets for the in vivo effect of alpha ASGM1 infusions (T cells or macrophages). We compared the effects of alpha ASGM1 infusions on alloantigen-stimulated T-cell proliferation versus antigen presentation: T-cell proliferation was markedly reduced by alpha ASGM1 infusions, whereas antigen presentation function was not diminished. We conclude that the mechanism whereby alpha ASGM1 prevents GVHD does not involve NK cells or antigen presenting cells, but does involve activated donor T cells. The potential therapeutic advantage of such an antibody for use in human disorders compared to pan-immunosuppression lies in its ability to eliminate selectively those T cells involved in the immunologic process (i.e. activated T cells) while sparing the remainder of the T-cell repertoire.

Cyclosporin A and the thymus. Immunopathology

Cyclosporin A (CsA) is known to diminish the size of the thymus, especially the thymic medulla. The significance of these changes is not presently understood. This study reveals several immunopathologic changes induced in the thymic medulla by CsA (15 mg/kg/day). The weight and relative size of the thymus dramatically and rapidly involutes, with marked changes observed in 1 week. The medullary thymocytes show segregation of rat T-cell phenotypes as seen in control rats, but the number of such cells is markedly reduced in accordance with the medullary remnant. This is consistent with a maturational arrest of thymocytes. The medullary epithelium was assessed directly by irradiating the control or CsA-treated rats 2 days prior to sacrifice. The epithelium of Hassall's corpuscles was essentially absent in CsA-treated rats but prominent in control rats. The cortical epithelial cells were preserved. Stains for Ia antigen with the anti-OX4 antibody show little change in expression by cortical epithelium, but a marked reduction in the Ia+ medullary cells in the thymocyte purged rats. All of these changes were reversible in the normal rat after cessation of CsA, with near normal recovery in 3 weeks. No morphologic or immunopathologic changes were noted in the cortical thymocytes. These cells did, however, acquire CsA receptors, as detected by the binding of fluorescent dansylated CsA.

Cell-mediated immunity in rheumatic disease

Rheumatoid arthritis, systemic lupus erythematosus, and systemic sclerosis are the three most common systemic rheumatic diseases in which disordered immune function is thought to play a pathogenetic role. Each disease has different and characteristic abnormalities of the cellular immune system. In rheumatoid arthritis the identified abnormalities of immunoregulation are largely limited to specific antigens: Epstein-Barr virus and collagen. Systemic lupus erythematosus is characterized by exuberant B-cell activity with exaggerated humoral response, a diversity of autoantibodies, non-antigen-specific loss of suppressor cell function, and general suppression of cell-mediated immunity. In systemic sclerosis systemic defects of cellular and humoral immune function are mild, but the release of lymphokines and monokines at sites of inflammatory lesions is thought to be important in the pathogenesis of the disease. Similar immune cell-connetive tissue cell interactions are probably important in the propagation of rheumatoid synovitis. Thus, despite the many shared clinical and serologic features of these diseases as well as the presence of many patients who have clinically overlapping features of more than one of these entities, the immune defects and the immunopathogenesis of these disorders appear to be distinct.

Animal model of human disease. Avian scleroderma. An inherited fibrotic disease of white Leghorn chickens resembling progressive systemic sclerosis

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Effect of the xid gene on graft-versus-host-induced autoantibody production in nonautoimmune mice

Graft-versus-host disease (GVH) was used to induce an autoimmune state in F1 recipients using donor spleen cells, splenic T cells, or Lyt 1+2- splenic T cells from either normal DBA/2 mice or from DBA/2 mice carrying the X-linked immunodeficiency (xid) gene. Recipients were either nondefective (DBA/2 X CBA/N)F1 males or reciprocal cross (CBA/N X DBA/2)F1 male mice carrying the xid gene. GVH induced hypergammaglobulinemia and anti-ssDNA autoantibodies in F1 recipients. Immunodeficient (CBA/N X DBA/2)F1 recipients had less hypergammaglobulinemia and IgG anti-ssDNA than did normal (DBA/2 X CBA/N)F1 recipients. Spleen cells, splenic T cells, and Lyt 1+2- splenic T cells from immunodeficient DBA/2.xid donors were less able to induce GVH and autoimmunity than normal DBA/2 donors. These studies suggest that the xid gene may reduce the autoimmune hyperractive state, but may do so by acting on more than one cell population, including T cells.

Chronic graft-versus-host disease as a model for scleroderma. II. Mast cell depletion with deposition of immunoglobulins in the skin and fibrosis

We explored the pathologic changes in the skin of mice undergoing a chronic graft-versus-host (GVH) reaction. In rodents and in man, chronic GVH includes the deposition of excess collagen in the skin-a reaction which resembles idiopathic scleroderma. GVH disease across minor histocompatibility barriers was produced by injecting B10.D2 cells into irradiated BALB/c mice. These strains are identical at the H-2 and Mls loci but differ in minor histocompatibility antigens. Control BALB/c mice received irradiation and BALB/c cells. Serial skin biopsies were taken and studied for histological changes characteristic of chronic GVHD, for mast cell density, and for the deposition of immunoreactants. GVHD was produced in B10.D2----BALB/c mice as measured by body weight loss and the production of skin changes including dermal fibrosis, loss of fat and appendages, and a mononuclear cell infiltrate. Dermal mast cells, assessed by toluidine blue staining, were normal at Day 11, but had disappeared by Days 21-63 and returned to normal by Day 104. Immunoglobulins IgG, IgA, and IgM appeared at the dermo-epidermal junction and along the basement membrane zone of hair follicles. This deposition was maximal at Day 42 and waned thereafter. Thus the appearance of immunoglobulins in the skin was maximal when mast cell staining was minimal. The changes in this GVHD model leading to a scleroderma-like picture in the skin are compatible with an immune etiology for the fibrosis. Vasodilation following liberation of mast cell mediators would facilitate the deposition of immunoglobulins. The disappearance of mast cell staining may be caused by extensive degranulation. We postulate an interaction between GVHD-activated T cells, mast cell stimulation, fibroblast activation, and fibrosis.

Mast cell depletion in murine chronic graft-versus-host disease

A murine model of chronic graft-versus-host disease (GVHD) was induced across minor histocompatibility barriers. This was done by injecting B10.D2 (H-2d) spleen cells into irradiated BALB/c (H-2d) mice. Chronic GVHD in this model includes features common to human idiopathic scleroderma, such as dermal fibrosis, loss of dermal fat and appendages, and a mononuclear cell filtrate. Serial skin biopsies showed a progressive loss of stainable mast cells in GVHD but not in irradiated controls. Mast cell depletion was noted as well in the tongue and kidney capsule of GVHD mice. Mast cell depletion was noted as early as 11 days after GVHD induction and persisted for at least 56 days. A hypothesis is put forth linking the T-cell activation of GVHD, mast cell degranulation, and increased fibrosis. The pertinence of this hypothesis to idiopathic scleroderma is pointed out.

Bone marrow transplantation in the rat. I. Histologic correlations and quantitation of cellular infiltrates in acute graft-versus-host disease

In an attempt to define which cytologic manifestations of inflammation are characteristic of acute graft-versus-host disease (aGVHD), the authors have analyzed hematologic reconstitution in the bone marrow, spleen, and blood of bone marrow transplant recipients and correlated these events to concomitant cytologic changes in the parenchymal target organs. After bone marrow transplantation from Lewis to BN strain, the strongest inflammatory changes were observed in the liver, a "model" parenchymal target organ for aGVHD in this strain combination. The inflammatory episode of the aGVHD in the liver was characterized by an early lymphoid blastogenesis, the presence of large granular lymphocytes (LGLs), lymphocytosis, and some monocytosis, lacking or significantly less prominent in the liver of syngeneic BN to BN recipients. Concomitantly with the infiltration of the liver with LGLs and lymphocytes, these cells were depleted from blood; and with their disappearance from the liver, they appeared in the recipient spleen. Lack of lymphoid blastogenesis in the bone marrow of allograft recipients and similar though less prominent cytologic changes in the syngeneic graft recipients, make it difficult to differentiate aGVHD-associated changes from normal reconstitution in the lymphoid tissue paper; the minimal changes in the blood make this organ the least suitable site for the monitoring of the aGVHD in the rat.

Human and murine cutaneous graft-versus-host diseases. Potential models for the study of immunologically mediated skin diseases

Cutaneous graft-versus-host disease in humans can be regarded as a potential model for the study of lymphocytotoxic reactions directed against the epidermis, and immunologically mediated cutaneous sclerosis. Toxic epidermal necrolysis and lichen planus are closely reproduced in graft-versus-host disease; sclerosis of chronic graft-versus-host disease cannot be regarded as strictly similar to any type of scleroderma. Sclerosis is the most consistently reproducible feature of cutaneous graft-versus-host disease in mouse chimeras; it offers the opportunity to study a dermal sclerosing reaction which may be considered as T cell dependent. Murine graft-versus-host disease presently appears debatable for use as a model of T cell dependent injury of the epidermis since stable established epidermal lesions are difficult to reproduce.

Scleroderma-like alterations in collagen metabolism occurring in the TSK (tight skin) mouse

Abnormalities in collagen metabolism similar to those occurring in the skin of patients with scleroderma have been demonstrated in the TSK (tight skin) mouse, a dominant mutant of the inbred B10.D2(58N)/SN mouse strain. These abnormalities, which consist of increased collagen content, accelerated biosynthesis, and increased extractibility of the newly synthesized molecules, suggest that the TSK mouse may be an excellent animal model for the study of the connective tissue alterations characteristic of scleroderma.

Murine graft-versus-host skin disease: a chronologic and quantitative analysis of two histologic patterns

Human graft-versus-host disease (GVHD) has several cutaneous manifestations, including a lichenoid and a sclerotic injury pattern. A versatile animal model of graft-versus-host skin disease (GVHSD) would facilitate study of the pathophysiology of these two cutaneous injury patterns. We have examined two murine chimeras histologically and have found two distinct patterns. Allogeneically transplanted B1/6 mice show a prolonged lichenoid-interface dermatitis that eventuates in clinical alopecia, whereas LP/J recipients of allogeneic cells do not show hair loss. Their histopathology consists of an early lichenoid phase that abates and is replaced by dermal sclerosis. Because of the versatility of the mouse as a laboratory animal, we feel that this model provides an excellent opportunity to define the immunopathologic mechanisms responsible for skin injury in GVHD. In addition, an understanding of the pathogenesis of the T cell-dependent, lichenoid, and sclerotic patterns of tissue injury in GVHSD might well provide insight into the pathogenesis of the GVHSD analogs, cutaneous lupus erythematosus and scleroderma.

Class II major histocompatibility antigens and the etiology of systemic lupus erythematosus

It is hypothesized that the underlying immunoregulatory dysfunction in systemic lupus erythematosus (SLE) is altered recognition by T cells of self class II major histocompatibility antigens (Ia). The resultant cellular autoreactivity would directly cause certain of the immunopathological manifestations of SLE. The perception by T cells of self non-MHC antigens in the context of altered Ia on antigen presenting cells would also stimulate specific help for autoantibody production. Autoimmunity induced by the graft-versus-host reaction is an experimental model that illustrates this potential mechanism (A. G. Rolink, S. T. Pals, and E. Gleichmann, J. Exp. Med. 157, 755, 1983; R. A. Eisenberg, S. Y. Craven, and P. L. Cohen, Arth. Rheum. 26, S19, 1983).

Chronic graft-versus-host disease (GVHD) as a model for scleroderma. I. Description of model systems

A model murine system of chronic graft-versus-host disease (GVHD) was explored to determine its suitability for studying scleroderma-like syndromes. The basic protocol was to inject lymphoid cell suspensions into irradiated semiallogeneic or allogeneic recipients which had been irradiated. Serial body weights, skin biopsies, and anti-nuclear antibodies were followed. Changes seen in the skin included increased collagen deposition, a mononuclear infiltrate deep in the dermis, loss of dermal fat, and "dropout" of skin appendages such as hair follicles. Body weight loss was a sensitive index of GVHD. Anti-nuclear antibodies occurred at times, but did not correlate with the tissue changes in the skin of mice undergoing GVHD. This chronic GVHD syndrome was produced across major and minor histocompatibility barriers. The most consistent findings were seen in BALB/c recipients of B10.D2 cells. These strains are nonreactive in unprimed mixed-leukocyte cultures. This combination represents primarily a GVH reaction against minor antigens where the HVG reaction is suppressed by irradiation. Some data suggest that the cutaneous changes may be reversible with time.

Induction of fibroblast proliferation by human mononuclear leukocyte-derived proteins

Human peripheral blood mononuclear leukocytes stimulated by T cell antigen or mitogen release soluble factors that induce mitogenesis of dermal fibroblasts in vitro. Fractionation of supernatants from antigen-stimulated mononuclear leukocyte cultures by Sephadex G-100 yielded 2 major peaks of fibroblast proliferation activity (approximately 60,000 and approximately 16,000 MW). Both proliferation factors are heat stable (56 degrees C for 45 minutes) proteins. These data show that mononuclear leukocytes, under appropriate conditions, can release soluble mediators that can stimulate fibroblast proliferation; such leukocytes may also play a role in expanding fibroblast populations adjacent to certain cell-mediated immune reactions in vivo.

Epidermal Langerhans cell involvement in cutaneous lupus erythematosus

Epidermal Langerhans cells (LCs) possess surface markers and functional attributes which identify them as being of macrophage/monocyte lineage, and recent evidence documents their participation in certain immune process which occur in skin. To assess the role of LCs in lupus erythematosus (LE), a disease in which immune system dysfunction predominates, human epidermis from patients with cutaneous LE was studied with 3 LC surface markers: ATPase activity, HLA-DR and OKT-6 antigens. Suction blister top epidermal skin biopsies from patients with 3 clinical types of cutaneous LE exhibited similar features: LCs were less dendritic, they were more irregularly distributed, and they were present in fewer numbers when compared with those in adjacent normal skin. These changes contrasted with those observed in diseases with similar lichenoid histopathological features. LCs appeared increased in number in lichen planus. LCs in skin lesions from one patient with dermatomyositis exhibited similar morphologic alterations, but surface densities and distributions were preserved. Disaggregated epidermal cells from skin lesions of patients with cutaneous LE induced allogeneic lymphocyte proliferation as efficiently as did cells from nonlesional skin, indicating that the morphologic alterations observed were not associated with a decreased alloantigen presenting capacity. These studies have demonstrated that epidermal LC populations in 3 clinical types of cutaneous LE are perturbed in a manner not seen in 2 other lichenoid skin diseases, although these changes were not associated with an altered capacity of such cells to stimulate proliferation by allogeneic lymphocytes.