Induction of cutaneous graft-versus-host disease by allo- or self-Ia-reactive helper T cells in mice

Importance of minor histocompatibility antigen expression by nonhematopoietic tissues in a CD4+ T cell-mediated graft-versus-host disease model

Minor histocompatibility antigens with expression restricted to the recipient hematopoietic compartment represent prospective immunological targets for graft-versus-leukemia therapy. It remains unclear, however, whether donor T cell recognition of these hematopoietically derived minor histocompatibility antigens will induce significant graft-versus-host disease (GVHD). Using established bone marrow irradiation chimeras across the multiple minor histocompatibility antigen-disparate, C57BL/6-->BALB.B combination, we studied the occurrence of lethal GVHD mediated by CD4+ T cells in recipient mice expressing only hematopoietically derived alloantigens. Even substantial dosages of donor C57BL/6 CD4+ T cells were unable to elicit lethal GVHD when transplanted into [BALB.B-->C57BL/6] chimeras. Instead, chimeric mice displayed transient cachexia with reduced target-tissue injury over time, reflecting an early, limited, graft-versus-host response. On the other hand, the importance of minor histocompatibility antigens derived from nonhematopoietic tissues was demonstrated by the finding that [C57BL/6-->BALB.B] chimeric mice succumbed to C57BL/6 CD4+ T cell-mediated GVHD. These data suggest that severe acute CD4+ T cell-mediated GVHD across this minor histocompatibility antigen barrier depends on the expression of nonhematopoietically rather than hematopoietically derived alloantigens for maximal target-tissue infiltration and injury.

Numerical, morphological and phenotypic changes in Langerhans cells in the course of murine graft-versus-host disease

BACKGROUND

In the course of graft-versus-host disease (GVHD) or diseases that histologically mimic GVHD (e.g. toxic epidermal necrolysis, Stevens-Johnson syndrome), it is known that epidermal Langerhans cells (LCs) are depleted from the epidermis. However, the mechanism and significance of LC depletion is not well known.

OBJECTIVES

To investigate the numerical, morphological and phenotypic changes in LCs and apoptosis of LCs in the course of GVHD using a non-irradiated mouse GVHD model.

METHODS

BALB/c nu/nu mice and C57BL/6 mice were used as recipients and donors, respectively. Recipient mice were injected with T-cell-enriched donor spleen cells. Skin samples were harvested at various times after the inoculation. The numerical and morphological changes were examined by an immunofluorescence study of epidermal sheets. Apoptosis was studied by the terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end labelling method and flow cytometric analysis using annexin V. Phenotypic change was studied by flow cytometric analysis of epidermal cell suspensions. The mixed epidermal cell lymphocyte reaction (MELR) was performed to examine functional changes in the epidermal cells.

RESULTS

Five days after inoculation, a graft-versus-host reaction occurred. Epidermal LCs began to decrease from the sixth day. On the fifth day, the LCs became larger and had prominent dendrites. Immediately before the LCs began to decrease, many LCs became round in shape, with scanty dendrites. LC apoptosis was not observed in the epidermis either on the fifth or seventh day. Phenotypically, the expression of CD40, CD80, CD86 and major histocompatibility complex class II antigen on the LCs was upregulated on the fifth and seventh day. Epidermal cells from GVHD mice showed an increased allostimulatory capacity in the secondary MELR.

CONCLUSIONS

These results suggest that at early GVHD onset, most LCs may not undergo apoptosis in the epidermis but are phenotypically activated, resulting in further activation of alloreactive T cells and aggravation of the disease.

Epidermal T cells: their functional role and disease relevance for dermatologists

T cells found within the epidermis in inflammatory dermatoses are generally accepted as making a major contribution to epidermal damage. On the other hand, those T cells residing in the murine epidermis are supposed to play an important role in protecting the epidermis from potentially dangerous immune reactions. Overwhelming evidence has accumulated that dendritic epidermal T cells (DETC) expressing monomorphic TCR gammadelta are responsible for the protection of epidermal structures against skin tumor, bacterial infection, and autoimmune attack. In animals congenitally lacking these gammadelta+ DETC, the epidermis is populated with bone marrow-derived TCR alphabeta+, CD8+ DETC. Although it remains unclear whether this subset of DETC could home to the epidermis to substitute for the physiologic function of gammadelta+ DETC or whether they would be pathologically relevant to epidermal injury, it should be noted that this subset represents the major fraction of T cells present in normal human epidermis and the most abundant in the lesional epidermis of fixed drug eruption (FDE). Because they are shown to kill target cells including keratinocytes upon stimulation and utilize a very limited range of TCR V alpha and Vbeta gene families, localized epidermal injury in FDE lesions would be mediated by activation of these epidermal T cells with autoaggressive potential. Epidermal T cells are thus likely to form several T-cell populations with different immunologic functions that are triggered by different modes of stimulation. Immune homeostasis in the epidermis would rely on a delicate balance between at least two types of epidermal T cells: autoaggressive T cells and protective T cells.

Expression of the T-Cell Activation Antigen, OX-40, Identifies Alloreactive T Cells in Acute Graft-Versus-Host Disease

The OX-40 molecule is expressed on the surface of recently activated T lymphocytes. The presence of OX-40 on CD4+ T cells was analyzed in a rat haplo-identical (parental → F1) bone marrow transplant model of acute graft-versus-host disease (aGVHD). Increased numbers of activated CD4+ T cells that expressed the OX-40 antigen were detected in peripheral blood soon after transplantation before the earliest sign of disease. The peak of OX-40 expression occurred 12 days posttransplantation with a range of 18% to 36% of circulating T cells and remained 10-fold above background, never returning to baseline. A slight increase in OX-40 expression (range, 1% to 6%) was also detected on peripheral blood lymphocytes from control syngeneic F1 → F1 recipients. OX-40+ T cells were isolated from spleen, skin, lymph node, and liver tissue of rats undergoing aGVHD, but not in syngeneic transplants. OX-40+ T cells isolated from these tissues were of donor origin and were shown to be allo-reactive. These data raise the possibility of using the OX-40 antibody to detect and deplete selectively the T cells that cause aGVHD.

Resistance to cutaneous graft-vs.-host disease is not induced in T cell receptor delta gene-mutant mice

The function of murine dendritic epidermal cells (dEC) remains largely speculative, probably because of the lack of a suitable in vivo model, although previous studies suggest that gamma/delta+ dEC may have originally evolved to serve as a self-protection mechanism(s). Our previous study demonstrated that the epidermis of mice that had spontaneously recovered from cutaneous graft-vs-host disease (GVHD) induced by local injection of CD4+ autoreactive T cells contained unexpectedly large numbers of dEC and became resistant to subsequent attempts to induce GVHD in a site-restricted manner, suggesting that the resistance is mediated by dEC. However, because alpha/beta+ dEC as well as gamma/delta+ dEC were greatly increased in number in the epidermis, it was unclear whether gamma/delta+ dEC are indeed responsible for this protection. The availability of this murine model and mice selectively lacking gamma/delta T cells as a result of disruption of the T cell receptor C delta gene segment allowed us to investigate the role of gamma/delta+ dEC. In the epidermis of gamma/delta T cell-deficient mice (delta-/-), a congenital lack of gamma/delta+ dEC was substituted for by alpha/beta+ dEC of either a CD4-8+ or a CD4-8- phenotype. After intradermal injection of the autoreactive T cells, delta-/- mice developed significantly enhanced delayed-type hypersensitivity responses and cutaneous GVHD, which persisted longer than in heterozygous littermate controls (delta+/-). Surprisingly, resistance to the cutaneous GVHD was not induced in the epidermis of delta-/- mice after spontaneous recovery from the GVHD, whereas the "susceptible" epidermis of delta-/+ mice contained large numbers of alpha/beta dEC comparable to those in "resistant" epidermis of delta+/- mice. Injection of day 16 fetal thymocytes from wild-type mice into delta-/- mice resulted in the appearance of donor-type gamma/delta+ dEC in the epidermis, and reconstitution with gamma/delta+ dEC restored the protective immune response of the epidermis against the GVHD to nearly normal levels. These results indicate that gamma/delta+ dEC are responsible for the site-restricted protection against cutaneous GVHD.

Immunohistological analysis of anti-melanoma host responses

Various clinical and experimental observations point to the existence of an immunological host defense in cutaneous malignant melanoma. To identify the major effector mechanisms mediating the specific anti-tumor immune response, we examined 23 benign and neoplastic melanocytic lesions (3 nevi, 14 primary melanomas, and 3 cutaneous and 3 systemic metastases) by quantitative immunohistology, and correlated these results with the histopathological and clinical subtypes of malignant melanoma. Our analyses indicate that CD3+ T-cell receptor alpha/beta-expressing lymphocytes are the prevailing leukocyte subset in primary as well as secondary malignant melanoma. We further observed that in early lesions (< 0.75 mm) of superficial spreading melanoma the vast majority of tumor-infiltrating lymphocytes (TIL) belong to the CD4+ subset and frequently express CD45RA antigens. In more advanced tumors, the contribution of CD8+ TIL gradually increases, indicating that the quality of the anti-tumor immune response changes during the course of the disease. Finally, we found that a varying percentage of cutaneous TIL express the cutaneous leukocyte antigen which is defined by the monoclonal antibody HECA 452 and preferentially expressed by skin-seeking memory T cells. In contrast, extracutaneous melanoma metastases (liver, brain, ovary) were completely devoid of HECA 452-reactive lymphocytes. These findings suggest that lymphocytes infiltrating cutaneous melanomas belong to a memory/effector T-cell subset functionally associated with the skin.

Immunoelectron microscopy of acute graft versus host disease of the skin after allogeneic bone marrow transplantation

AIMS

To clarify the pathological mechanisms of acute cutaneous graft versus host disease (GvHD) following allogeneic bone marrow transplantation.

METHODS

Skin biopsy specimens from five patients were examined by immunoelectron microscopy. A panel of monoclonal antibodies against T cell and natural killer cell subpopulations was used, including anti-CD4, -CD8, -CD16b, -CD56, -CD57, and -TCR delta 1 antibodies.

RESULTS

All the specimens contained CD8+ cells, CD4+ cells, and CD56+ cells infiltrating the epidermis. Cells stained with anti-CD16b, -CD57, or -TCR delta 1 were very sparse or absent. Most of the CD8+ cells in the epidermis displayed morphological features of activated cytotoxic T lymphocytes and apposition of such cells to degenerating keratinocytes was shown. CD4+ cells outnumbered CD8+ cells in the epidermis in all five cases. Noticeable intercellular as well as intracellular oedema of keratinocytes was observed at the site of prominent CD4+ cell infiltration, suggesting that these also have a role as actual effector cells by secreting cytotoxic cytokines. CD56+ cells infiltrating the epidermis did not exhibit the characteristic ultrastructural morphology of the natural killer cells thus far examined, and their lineage remained uncertain.

CONCLUSIONS

These data provide direct evidence that CD8+ cytotoxic T cells attack keratinocytes, and further suggest that CD4+ cells as well as CD56+ cells participate in the cellular pathogenesis of acute cutaneous GvHD.

Auto-MHC class II-reactive T cell line obtained from MRL/+ mice suffering from lpr-GVHD. II. Analyses of functional characteristics of T cell line by in vivo administration

Functional characteristics of an autoreactive (I-Ek-restricted) T cell line (l/+ T1), previously established from MRL/M(p-)+/+(MRL/+) mice with lpr-GVHD, were analyzed in vivo. Intravenous injection of l/+ T1 cells to non-irradiated H-2k (MRL/+ or AKR) mice (but not H-2d mice) induced enhanced spontaneous proliferation of recipient spleen cells; this was also I-Ek self-restricted. This augmented self-reactivity seemed to be mediated by recipient L3T4+ T cells, since few l/+ T1 cells were detected in the spleen cells of l/+ T1-injected AKR mice by cell surface marker analyses, and the treatment of the spleen cells with anti-Thy-1.1 antibody (Ab) or anti-L3T4 Ab plus complement abolished this enhanced spontaneous proliferation. The production of IgM rheumatoid factor (RF) in AKR mice and IgG RF in MRL/+ mice increased, although no enhancement of anti-ssDNA Ab production was observed. Judging from both spleen B cell proportion and serum Ig levels, autoantibody induction by the injection of l/+ T1 cells was not associated with polyclonal B cell activation. When lethally irradiated B10 congenic mice were used as recipients, B10. BR mice showed elevated levels of IgM anti-ssDNA and IgM RF 1 wk after l/+ T1 cell injection; it is likely that lethal irradiation causes autoantigens, particularly DNA, to be exposed. These findings suggest that the autoreactivity of l/+ T1 cells can be transferred to recipient L3T4+ T cells via T-T interaction or the immunological network, and that increased autoreactivity induces autoantibody production in the presence of autoantigen stimulation. In contrast to the stimulatory effects observed in AKR and MRL/+ mice, MRL/Mp-lpr/lpr(MRL/lpr) mice showed a different response to the injection of l/+ T1 cells; spontaneous proliferation of spleen cells and autoantibody production were not enhanced, and suppression of the mitogen responses was observed. It is discussed that lpr-GVHD may be due to these unusual features of MRL/lpr mice.

Induction of cutaneous graft-versus-host disease by local injection of unprimed T cells

The skin is a major target organ in human graft-versus-host disease (GVHD) after bone-marrow transplantation. GVHD can be induced in mice by i.v. injection of T cells into unirradiated semi-allogeneic or lethally irradiated allogeneic recipients. However, in the murine systemic GVHD model, cutaneous lesions occur only in lethally irradiated recipients. Since lethal irradiation itself might induce the epidermal cell damage, several investigators have employed another murine model of cutaneous GVHD, in which cutaneous lesions were induced by intradermal injection of alloreactive T cell clones. Using this system, it has been reported that both MHC class I- and II-reactive T cell clones can induce cutaneous GVHD in non-irradiated or sublethally irradiated recipients. However, it has remained unknown whether or not freshly prepared T cells are able to induce cutaneous GVHD after local injection into non-irradiated recipients. We show that unprimed T cells can induce cutaneous GVHD after local injection into unirradiated MHC class II- or I + II-disparate recipients. In contrast to alloreactive T cell clones, unprimed T cells could elicit only mild cutaneous lesions in MHC class I-disparate recipients. Since sublethal irradiation of MHC class I-disparate recipients did not result in the manifestation of cutaneous lesions after injection of unprimed T cells, host anti-donor responses by radiosensitive cells could not be responsible for this phenomenon. This experimental system provides a useful model for analysis of the regulation mechanisms in the induction of GVHD by unprimed T cells.

Graft-versus-host reactions in the rat mimic toxin-induced autoimmunity

Gold salts, D-penicillamine or mercurials induce autoimmunity in Brown Norway (BN) rats and provoke an immunosuppression in Lewis (LEW) rats. It has been suggested that immunologically mediated manifestations induced by drugs could result from graft-versus-host (GVH) like reactions. We show that BN spleen cells transferred into (LEW x BN)F1 hybrids induce a chronic GVH reaction (GVHR). This reaction led to an autoimmune disease quite similar to that induced by drugs in BN rats. In both situations, a common part of the B cell repertoire is triggered. In contrast, LEW spleen cells transferred into (LEW x BN)F1 hybrids provoke a lethal GVHR. This is to be compared with the CD8-mediated immunosuppression observed in LEW rats injected with HgCl2. These findings are in agreement with the prediction that immune dysregulation induced by drugs leads to GVH-like reactions either stimulatory or suppressive depending upon the strain tested.

Loss of epidermal integrity by T cell-mediated attack induces long-term local resistance to subsequent attack. I. Induction of resistance correlates with increases in Thy-1+ epidermal cell numbers

The cutaneous graft-versus-host disease (GVHD) lesions induced by intradermal injection of cloned autoreactive T cells have been shown to subside rapidly and the epidermis returns to normal 2 wk after injection. Those mice that had spontaneously recovered from the cutaneous GVHD became resistant to subsequent attempts to induce the cutaneous GVHD by the T cells while maintaining their activity to mount delayed-type hypersensitivity (DTH) responses and to induce the enlargement of the popliteal lymph nodes (PLN). The resistance appeared to be restricted to the epidermal structures of the injection sites, suggesting the involvement of locally acting suppression mechanisms. This local resistance was not specific for the clonotype used for the induction of the resistance. A loss of the epidermal integrity by an attack of T cells capable of producing cutaneous GVHD was a prerequisite for the induction of the resistance. By up to at least 8 mo after injection of the T cells, no mice became susceptible to the cutaneous GVHD again, provided that the T cells were injected into the same footpad sites that had initially received the T cells. This resistance correlated well with the great increase (20-30-fold) in Thy-1+ EC number. The great increase in the number of Thy-1+ EC following destruction of epidermal structures may be important in protecting the epidermal integrity from an additional attack by T cells.

Differential expression of lymphocyte function-associated antigen 1 (LFA-1) on epidermotropic and non-epidermotropic T-cell clones

Various T-cell surface molecules are involved in T-cell adhesion, which is an essential requirement for epidermotropic migration of T cells. Our previous studies demonstrated that certain T-cell clones can migrate into the epidermis upon their intradermal inoculation into the footpads of recipient mice with relevant antigens, while other T-cell clones, despite their identical antigen specificities and functions, are non-epidermotropic. We therefore tested whether the differences in epidermotropism of these T cells could reside in the different levels of expression of T-cell surface molecules such as CD3, CD4, CD2, and lymphocyte function associated antigen 1 (LFA 1). The results of flow cytometric analysis showed that LFA-1 was preferentially expressed on the surface of epidermotropic T-cell clones, while non-epidermotropic T-cell clones were negative or very weakly positive for LFA-1 with one exception. After exposure to phorbol ester, epidermotropic clones with high levels of LFA-1 did not show any further up-regulation of LFA-1. In contrast, under identical conditions, significant up-regulation of LFA-1 was observed on non-epidermotropic T cells with low levels of LFA-1. However, even after exposure to phorbol ester, these T cells remained non-epidermotropic. These results suggest that the presence of high levels of LFA-1 on T cells is absolutely necessary for their epidermotropic migration, but its up-regulation is neither necessary nor sufficient to trigger the epidermotropic migration. High levels of LFA-1, regardless of cell activation, may be required to mediate stable cell adhesions leading to epidermotropic migration.

Graft-versus-host disease: an alternative hypothesis

Medawar and Billingham in their classic experiments described three prerequisites for the development of graft-versus-host disease (GVHD): first, the presence of immunocompetent cells in the donor inoculum; second, the inability of the recipient to reject the donor cells; and third, a histocompatibility difference between the donor and recipient. These experiments are the basis for all later hypotheses related to the pathogenesis of GVHD. Recently, de Gast and colleagues reviewed the role of environmental antigens in the pathogenesis of GVHD and suggested that immunological responses to environmental antigens by the transplanted donor cells might contribute to an increased donor anti-recipient response. An area not addressed in that review was the potential role of autoreactivity in GVHD. In this short article, Robertson Parkman highlights the role of autoreactivity and autoantigens in the pathogenesis of both acute and chronic GVHD in histocompatible bone marrow transplantation.

In vitro migration of L3T4+ cloned T cells to epidermis: possible role for keratinocyte-derived factors

Three types of L3T4+ cloned T cells with different antigen specificities, auto-, allo-, and antigen-reactive, were characterized with respect to their migratory potential using an in vitro migration assay under agar gel. Autoreactive T cells, BB5, and alloreactive T cells, SK 1, both of which have been proved to be epidermotropic in vivo, showed specific directional migration to the epidermis, whereas no directional migration was seen with non-epidermotropic cloned T cells and freshly isolated lymph node T cells. Both BB5 and SK 1 cells were equally attracted to all the epidermal fragments tested regardless of their I-A antigens. The directional migration of BB5 cells to the epidermis was significantly inhibited by the co-cultivation with the epidermis, but not the dermis. Studies with cell lines, the conditioned media (CM), and recombinant interleukin (IL) 1, 2, and 3 revealed that BB5 cells were chemotactically attracted to a transformed keratinocyte cell line PAM212 and, to a lesser extent, to the CM from PAM212 and IL-2, but not to IL-1 and IL 3. These results suggest that epidermotropic T cells may be preferentially trapped in an area with a high concentration of keratinocyte-derived growth factors as well as IL-2.

Lichenoid tissue reaction induced by local transfer of Ia-reactive T-cell clones. III. Role of Ia+ keratinocytes in the epidermotropic migration of the T cells

The role of Ia+ keratinocytes in epidermotropism of T cells was analyzed by using self-IA specific autoreactive cloned T cells with epidermotropic nature (termed BB5) and those without it (termed C10). These T-cell clones were injected into the footpads of syngeneic nude mice whose keratinocytes had been induced to express Ia by the iv injection of normal mouse serum. Ia expression by keratinocytes was associated with the increased epidermal invasion of BB5 cells, but did not render C10 cells capable of migrating into the epidermis. The migration of the T cells to epidermis was also studied in vitro using a migration assay under agar. Ia expression by keratinocytes significantly enhanced the in vitro migration of BB5 cells to the epidermis, but had no effect on the migration of C10 cells and freshly isolated unstimulated lymphocytes. We surmise from these results that Ia+ keratinocytes may facilitate the epidermal invasion of the T cells with epidermotropic nature, but not those without it. However, the possibility certainly exists that the observed preferential migration of BB5 cells to Ia+ keratinocytes may be secondary to the alteration of other factors associated with the Ia expression. The injection of normal mouse serum was accompanied by an increase in the production of epidermal cell-derived thymocyte activating factor (ETAF) indicating that the increased ETAF production may have contributed to some of the observed preferential migration of BB5 cells.