Suppression of cytotoxic T lymphocyte activity by gamma/delta T cells in tumor-bearing mice

Tumor formation initiated by nondividing epidermal cells via an inflammatory infiltrate

In mammalian epidermis, integrin expression is normally confined to the basal proliferative layer that contains stem cells. However, in epidermal hyperproliferative disorders and tumors, integrins are also expressed by suprabasal cells, with concomitant up-regulation of Erk mitogen-activated protein kinase (MAPK) signaling. In transgenic mice, expression of activated MAPK kinase 1 (MEK1) in the suprabasal, nondividing, differentiated cell layers (InvEE transgenics) results in epidermal hyperproliferation and skin inflammation. We now demonstrate that wounding induces benign tumors (papillomas and keratoacanthomas) in InvEE mice. By generating chimeras between InvEE mice and mice that lack the MEK1 transgene, we demonstrate that differentiating, nondividing cells that express MEK1 stimulate adjacent transgene-negative cells to divide and become incorporated into the tumor mass. Dexamethasone treatment inhibits tumor formation, suggesting that inflammation is involved. InvEE skin and tumors express high levels of IL1α; treatment with an IL1 receptor antagonist delays tumor onset and reduces incidence. Depletion of γδ T cells and macrophages also reduces tumor incidence. Because a hallmark of cancer is uncontrolled proliferation, it is widely assumed that tumors arise only from dividing cells. In contrast, our studies show that differentiated epidermal cells can initiate tumor formation without reacquiring the ability to divide and that they do so by triggering an inflammatory infiltrate.

The current status and future direction of percutaneous peptide immunization against melanoma

Dendritic cell (DC)-based tumor immunotherapy is widely known to elicit protective anti-tumor immune responses, although the safety and effectiveness have yet to be thoroughly explored. We reported that a disruption in the stratum corneum barrier resulted in enhanced permeability and alterations in the skin immune system in such a way that epidermal Langerhans cells (LCs) functioned as vigorous antigen presenters for T helper (Th) cells and cytotoxic T lymphocytes (CTLs). In both human and murine models, topical application of melanoma-associated antigen peptides onto stratum corneum barrier-disrupted skin, specifically induced tumoricidal immune responses in vivo and in vitro accompanying an increased expression of MHC and co-stimulatory molecules on LCs. In addition, for reasons of simplicity, safety and effectiveness, percutaneous peptide application has demonstrated a certain degree of feasibility in clinical approach in patients with melanoma. In the future, resolution of some of the outstanding issues concerning the selection of the most effective adjuvants in combination with barrier disruption and depletion of regulatory T (Treg) cell-mediated immune suppression would appear as essential to improve percutaneous melanoma immunotherapy.

Gammadelta T cells promote anterior chamber-associated immune deviation and immune privilege through their production of IL-10

Anterior chamber-associated immune deviation (ACAID) is a form of peripheral tolerance that is induced by introducing Ags into the anterior chamber (AC) of the eye, and is maintained by Ag-specific regulatory T cells (Tregs). ACAID regulates harmful immune responses that can lead to irreparable injury to innocent bystander cells that are incapable of regeneration. This form of immune privilege in the eye is mediated through Tregs and is a product of complex cellular interactions. These involve F4/80+ ocular APCs, B cells, NKT cells, CD4+CD25+ Tregs, and CD8+ Tregs. gammadelta T cells are crucial for the generation of ACAID and for corneal allograft survival. However, the functions of gammadelta T cells in ACAID are unknown. Several hypotheses were proposed for determining the functions of gammadelta T cells in ACAID. The results indicate that gammadelta T cells do not cause direct suppression of delayed-type hypersensitivity nor do they act as tolerogenic APCs. In contrast, gammadelta T cells were shown to secrete IL-10 and facilitate the generation of ACAID Tregs. Moreover, the contribution of gammadelta T cells ACAID generation could be replaced by adding exogenous recombinant mouse IL-10 to ACAID spleen cell cultures lacking gammadelta T cells.

Impaired CD40-signalling in Langerhans' cells from murine neonatal draining lymph nodes: implications for neonatally induced cutaneous tolerance

Cutaneous tolerance to antigens may be induced in mice through application of antigen during the first few days following birth. The mechanism governing this neonatally induced tolerance remains uncertain. We employed a contact hypersensitivity model to analyse dendritic cell (DC) function and the expression of classical and non-classical lymphocyte populations within the neonate. Examination of draining lymph node DC after antigenic challenge of the skin revealed these DC to be significantly deficient in their ability to stimulate antigen-specific T cell proliferation. Co-stimulatory molecule (CD40, CD80 and CD86) expression of these cells was deficient in comparison to adult DC, and functional tests revealed these cells to possess a critical absence of CD40 signalling. A numerical analysis of classical and non-classical lymphocyte expression demonstrated that while the neonatal spleen is devoid of T cells, the lymph nodes have a normal repertoire of T, B, gammadelta and CD4+CD25+ lymphocytes but an increased expression of natural killer (NK) cells. This study indicates that functionally deficient DC are likely contributors to neonatally induced cutaneous tolerance.

Inhibition of tumor rejection by gammadelta T cells and IL-10

Although many tumors express tumor-specific antigens, most fail to stimulate effective immune responses. Tumors generally lack co-stimulatory molecules, which can lead to tolerance of tumor-specific T cells and progressive tumor growth. Here, we demonstrate that the ovalbumin (OVA) transfected EL4 tumor, E.G7-OVA, grows progressively in syngeneic mice even though the tumor can be rejected if the mice are immunized with OVA in adjuvant. E.G7-OVA grew more rapidly in RAG-1 deficient than sufficient mice suggesting that normal mice make an abortive immune response to this tumor. Depletion of gammadelta T cells or IL-10 augmented the ability of B6 mice to reject E.G7-OVA. Spleen cells from normal, but not IL-10 knockout, mice reconstituted rapid tumor growth in gammadelta T cell-deficient mice. Thus, gammadelta T cells play an important role in preventing immune elimination of this tumor by a mechanism that directly or indirectly involves IL-10.

Mechanisms of immune privilege for tumor cells by regulatory cytokines produced by innate and acquired immune cells

In murine tumors, innate immunity act as a trigger for the development of acquired immunity. The innate immune cells, natural killer (NK) and natural T (NKT) cells, generate the acquired immune cells, cytotoxic T lymphocytes (CTLs) and T helper (Th) 1 cells, by releasing interferon (IFN)-gamma. Regulatory T cells co-infiltrate with these tumoricidal effectors. In the innate phase, T cell receptor (TCR) gammadelta-bearing T (gammadelta T) and TCRalphabeta intermediate T cells are the regulators that suppress NK and NKT cells by elaborating interleukin (IL)-4, IL-10 and transforming growth factor (TGF)-beta. The acquired phase has Th3/T regulatory 1-like cells that inhibit CTLs and Th1 cells by TGF-beta. Thus, cytokines from regulatory T cells exert profound effects on tumor growth.

Phenotypic analysis of oral tolerance to alloantigens: evidence that the indirect pathway of antigen presentation is involved

BACKGROUND

Oral administration of alloantigens induces down-regulation of Th1 immune responses and reduces the incidence of corneal graft rejection. This study examined the role of Th1 and Th2 cytokines, accessory cells, and lymphoid organs that are known to be instrumental in other forms of antigen-specific tolerance.

METHODS

Allogeneic dendritic cells (DC) were administered orally using a protocol that is known to reduce the incidence of corneal allograft rejection and prevent the generation of allospecific delayed-type hypersensitivity (DTH). Hosts included normal mice and gene knockout (KO) mice, including B cell-deficient (mu)MT, interleukin (IL)-4 KO, IL-10 KO, and interferon (IFN)-gamma KO mice. The requirement for either an intact spleen or thymus was also examined. Orally administered paraformaldehyde-fixed, UVB-treated, or sonicated allogeneic cells were tested to determine if dead cells were capable of inducing tolerance.

RESULTS

Studies on gene KO mice indicated that a Th1 cytokine (IFN-gamma) and a Th2 cytokine (IL-4) were needed for the development of oral tolerance to alloantigens. By contrast, IL-10 was not required. Although an intact spleen was necessary for the development of tolerance, removal of the thymus did not affect down-regulation of DTH.

CONCLUSIONS

Oral tolerance induced with allogeneic cells shares characteristics with antigen-specific unresponsiveness induced by other routes, yet there are some noteworthy differences. The capacity of killed or sonicated allogeneic cells to induce oral tolerance and enhance corneal graft survival indicates that oral tolerance to alloantigens can occur via the indirect pathway of alloantigen presentation. These results also emphasize the remarkable redundancy in the mechanisms that the immune system employs to produce antigen-specific unresponsiveness.

Enhanced formation of azoxymethane-induced colorectal adenocarcinoma in gammadelta T lymphocyte-deficient mice

T cell receptor (TCR) gammadelta-positive T lymphocytes, which are localized mostly within the intraepithelial space of intestinal epithelium, have been suggested to play a role in maintaining the normal configuration of intestinal epithelium. However, the role of TCRgammadelta-positive T lymphocytes in the formation and progression of colorectal adenocarcinoma that originates from colorectal epithelial cells remains to be elucidated. In this study, TCRalphabeta and TCRgammadelta-positive T lymphocyte-deficient mice (homozygous TCRa and TCRd-gene knockout mice) and the background wild-type mice were administered azoxymethane, and the formation of macroscopic tumors and microscopic aberrant crypt foci in colorectal mucosa were compared among the three types of mice. Well-differentiated adenocarcinoma appeared 5 months after 5 administrations of azoxymethane (10 mg/kg weight) only in a few TCRd -gene knockout mice and the frequency of the carcinoma-bearing mice was increased at 7 and 9 months after the administration. Aberrant crypt foci were also detected in the colorectal mucosa of TCRd -gene knockout mice to a greater extent than in colorectal mucosa of TCRa-gene knockout mice 1 month after the azoxymethane administration. These results suggest that TCRgammadelta-positive T lymphocytes, which are present mainly in the intraepithelial space, play a role in suppression of the formation and progression of colorectal adenocarcinoma in mice.

Interleukin-10 expressed at early tumour sites induces subsequent generation of CD4(+) T-regulatory cells and systemic collapse of antitumour immunity

We investigated the relationship between transforming growth factor-beta (TGF-beta)-secreting T-regulatory (Tr) cells and anti-B16 melanoma immunity, and studied the association of early cytokines expressed at tumour sites with the generation of Tr cells. A large number of CD4(+) Tr cells producing interleukin (IL)-4, IL-10 and TGF-beta accumulated with functionally depressed CD8(+) cytotoxic T lymphocytes (CTLs) at tumour sites on day 20 after subcutaneous (s.c.) inoculation of B16 tumour cells. Tr cells consisted of two populations, which were termed T helper 3 (Th3) and Tr1 cells. B16-infiltrating Tr cells strongly inhibited the generation of B16-specific T helper 1 (Th1) cells in a TGF-beta-dependent manner and were assumed to suppress effective generation of CTLs. In addition, B16 cells markedly progressed in mice transferred adoptively by the cultured B16-infiltrating Tr cells compared with untreated mice. The capacity of these Tr cells to produce TGF-beta was hampered by neutralizing anti-IL-10 and partly anti-IL-4 monoclonal antibodies (mAbs) injected intralesionally during the early development of B16 tumours, and this treatment markedly attenuated B16 growth. Furthermore, a lesional injection of recombinant mouse IL-10 at an early tumour site resulted in the vigorous progression of B16 tumours. These results provide evidence that Tr cells, belonging to the T helper 3/T-regulatory 1 (Th3/Tr1) type, are activated in B16-bearing hosts under the influence of T helper 2 (Th2) cytokines, mainly IL-10 (produced at early tumour lesions), and that this regulatory T-cell population functions as a suppressor of anti-B16 immunity.

Gamma delta T cells are needed for ocular immune privilege and corneal graft survival

It has been recognized for over a century that the anterior chamber of the eye is endowed with a remarkable immune privilege. One contributing component is the Ag-specific down-regulation of systemic delayed-type hypersensitivity (DTH) that is induced when Ags are introduced into the anterior chamber. This phenomenon, termed anterior chamber-associated immune deviation (ACAID), culminates in the generation of regulatory cells that inhibit the induction (afferent suppression) and expression (efferent suppression) of DTH. Since gamma delta T cells play a major role in other forms of immune regulation, we suspected they might contribute to the induction and expression of ACAID. Mice treated with anti-gamma delta Ab failed to develop ACAID following anterior chamber injection of either soluble Ag (OVA) or alloantigens (spleen cells). Additional experiments with knockout mice confirmed that mice lacking functional gamma delta T cells also fail to develop ACAID. Using a local adoptive transfer of DTH assay, we found that gamma delta T cells were required for the generation of regulatory T cells, but did not function as the efferent regulatory cells of ACAID. The importance of gamma delta T cells in corneal allograft survival was confirmed by blocking gamma delta T cells with GL3 Ab before corneal transplantation. While in vivo treatment with normal hamster serum had no effect on corneal graft survival, infusion of anti-gamma delta Ab resulted in a profound increase in corneal allograft rejection. Thus, gamma delta T cells are needed for sustaining at least one aspect of ocular immune privilege and for promoting corneal allograft survival.

Circulating and tumor-infiltrating gamma delta T Cells in patients with B-cell lymphomas

In order to analyze the involvement of gamma delta T cells in the immune surveillance against B cell lymphomas (BCL), we investigated the proportion of circulating gamma delta T cells in 52 BCL patients using two-color flow cytometry, together with tumor-infiltrating gamma delta T cells in 22 of those patients. We found that the proportion of tumor-infiltrating gamma delta T cells in BCL patients was not different from that of lymph node gamma delta T cells in reactive hyperplasia patients. However, a decreased percentage of circulating gamma delta T cells were observed in indolent lymphoma (IL) and limited aggressive lymphoma (AL) patients when compared with normal controls. In contrast, as a result of a histogram, advanced AL patients were divided into two subgroups: the patients with increased circulating gamma delta T cells and those without any increase. However, there was no difference in the clinical features of between the two AL subgroups.

Disordered expression of inhibitory receptors on the NK1-type natural killer (NK) leukaemic cells from patients with hypersensitivity to mosquito bites

Recent studies have revealed the existence of a distinct type of NK cell leukaemia of the juvenile type, which presents with hypersensitivity to mosquito bites (HMB) as an essential clinical manifestation and is infected with clonal Epstein-Barr virus (EBV). This disorder is thus called HMB-EBV-NK disease and has been reported in Orientals, mostly from Japan. We investigated the profile of cytokine production and the expression of both types of NK inhibitory receptors, i.e. CD94 lectin-like dimers and killer-cell immunoglobulin-like receptors, in NK leukaemic cells from three patients with HMB-EBV-NK disease. It was found that freshly isolated NK leukaemic cells expressed mRNA for interferon-gamma (IFN-gamma) and additionally produced IL-10 upon stimulation with IL-2, indicating that the NK cells were of NK1 type. More than 98% of NK cells from the patients bore CD94 at a higher level than did normal NK cells, whereas p70 or NKAT2, belonging to immunoglobulin-like receptor, was not expressed in those NK cells. Freshly isolated leukaemic NK cells transcribed mRNA for CD94-associated molecule NKG2C at an abnormally high level, and upon stimulation with IL-2 and/or IL-12 they expressed NKG2A as well. The disordered expression of these inhibitory receptors not only provides some insights into the pathogenesis of HMB-EBV-NK disease but also can be used as phenotypic markers for the diagnosis of this type of NK cell leukaemia.

Percutaneous peptide immunization via corneum barrier-disrupted murine skin for experimental tumor immunoprophylaxis

H-2K(b)-restricted tumor epitope peptides, including tyrosinase-related protein 2 residues 181-188 (TRP-2) and connexin 37 residues 52-59 (MUT1), were applied to permeability barrier-disrupted C57BL/6 (B6) mouse skin from which the stratum corneum of the epidermis had been removed by tape-stripping. This procedure primed tumor-specific cytotoxic T lymphocytes (CTLs) in the lymph nodes and spleen, protected mice against subsequent challenge with corresponding tumor cells, and suppressed the growth of established tumors. Preventive and therapeutic effectiveness was correlated with the frequency of tumor-specific CTL precursors. MHC class II Ia(b+) cells separated from tape-stripped skin, compared with those from intact skin, exhibited a strong antigen-presenting capacity for CTL, suggesting that CTL expansion after peptide application is primarily mediated by epidermal Langerhans cells. Thus, percutaneous peptide immunization via barrier-disrupted skin provides a simple and noninvasive means of inducing potent anti-tumor immunity which may be exploited for cancer immunotherapy.

Role of interleukin-4 in down-regulation of contact sensitivity by gammadelta T cells from tolerized T-cell receptor alpha-/- mice

Contact sensitivity (CS) is a classical example of an in vivo T-cell-mediated immune response that is under regulation. Such down-regulation can be mediated by alphabeta T cells in mice that are tolerized by prior exposure to high doses of antigen. In contrast, we demonstrated previously that such high-dose antigen tolerance in T-cell receptor (TCR) alpha-/- H-2d mice induced antigen-specific, apparently major histocompatibility complex-unrestricted, CD4- CD8- gammadelta T cells, that also could down-regulate CS responses antigen-specifically in vivo, and also inhibited in vitro production of IFN-gamma. In the present experiments we employed H-2b-deficient TCRalpha-/- and TCRbeta-/- mice, owing to different molecular constructs than were used previously, and confirmed that tolerized gammadelta T cells in these different H-2b alphabeta TCR-/- mice down-regulated CS. Thus, gammadelta T-cell suppressor function was not limited to mice bearing a special transgenic TCRalpha-/- DNA construct. Furthermore, employing monoclonal antibody and complement depletion in vitro and adoptive transfer in vivo, characterized the phenotype of these gammadelta down-regulatory T cells as: CD3+, CD28+, CD40-ligand+, Fas+, FcgammaR+ and NK1.1-. Also, in vitro antigen desensitization of these trinitrophenyl (TNP)-specific TCRgammadelta+ down-regulatory cells was achieved with soluble TNP-bovine serum albumin (BSA), but not with oxazolone-BSA, showing that these suppressive gammadelta T cells have antigen-specific receptors. Moreover, employing monoclonal antibody blocking of gammadelta suppressors in vitro, and of recipients in vivo, we showed that interleukin-4 (IL-4) was involved in this down-regulation of CS by gammadelta T cells, while IL-10 and transforming growth factor-beta2 were not. In summary, generation of antigen-specific, double-negative, gammadelta suppressor cells, by tolerance of high antigen doses in TCRalpha-/- mice, appears to be a general phenomenon, and IL-4 production is involved in their down-regulation of the T helper type 1 cells that mediate CS.

Depletion of IL-10- and TGF-β-Producing Regulatory γδ T Cells by Administering a Daunomycin-Conjugated Specific Monoclonal Antibody in Early Tumor Lesions Augments the Activity of CTLs and NK Cells

It has been demonstrated that γδ T cells accumulating in early tumor lesions and those purified from spleen cells of tumor-bearing mice attenuate the activity of CTLs and NK cells. We, therefore, investigated whether depletion of γδ T cells from early lesions of tumors results in restoration of CTL and NK cell activities and subsequent regression of tumors. A daunomycin-conjugated anti-γδTCR mAb UC7-13D5 (Dau-UC7) was prepared to efficiently deplete γδ T cells. An in vitro study revealed that Dau-UC7 specifically lysed γδTCR+ cells and effectively inhibited splenic γδ T cells from tumor-bearing mice to produce cytotoxic cell-suppressive factors. Furthermore, intralesional injections of Dau-UC7 at an early stage of tumor development led to augmentation of tumor-specific CTL as well as NK cell activities and to the resultant regression or growth inhibition of the tumors. On analysis of cytokine profile, γδ T cells transcribed mRNAs for IL-10 and TGF-β, but not IL-4 or IFN-γ, suggesting the T regulatory 1-like phenotype. Finally, a blocking study with mAbs showed that the inhibitory action of γδ T cells on CTLs and NK cells was at least partly mediated by IL-10 and TGF-β. These results clearly demonstrated the novel mechanism by which T regulatory 1-like γδ T cells suppress anti-tumor CTL and NK activities by their regulatory cytokines in early tumor formation.

Downregulation of innate and acquired antitumor immunity by bystander gammadelta and alphabeta T lymphocytes with Th2 or Tr1 cytokine profiles

It has been thought that natural killer (NK) cells appearing early in tumor lesions play a pivotal role in the innate immunity against tumor cells. Although NK cells serve as the first tumoricidal effector cells, they subsequently promote a shift in effectors from themselves to tumor-specific cytotoxic T lymphocytes (CTLs) that mediate the acquired immunity. The mechanism of this shift has not been fully elucidated, however, NK cell-derived T helper (Th) 1 cytokines such as interferon (IFN)-gamma seem to play a key role. Another NK-lineage, termed natural killer T (NK T) cells, may also participate in the innate period when they acquire the ability to secrete Th1 cytokines. Interleukin-4 (IL-4) and IL-10, belonging to Th2, and transforming growth factor-beta (TGF-beta), belonging to T regulatory (Tr) 1 cytokines, are known to suppress the development of NK, NK T cells, as well as CTLs and to block Th0 cell differentiation to Th1 cells, suggesting that tumor cells can evade the innate and acquired immunity by virtue of cells producing these inhibitory cytokines. In early tumor lesions of murine B16 melanoma, gammadelta T and alphabeta intermediate (int) T cells that co-infiltrate with NK and NK T cells can produce Th2 cytokines and inhibit the innate immunity. In MM2 mammary tumor-bearing mice, gammadelta T cells appearing both lesionally and systemically secrete Tr1-type cytokines and depress the acquired immunity. These Th2- or Tr1-type gammadelta T and alphabeta(int) T cells downregulate the tumoricidal cells by means of both their secreted cytokines and express major histocompatibility complex (MHC) class I molecules.

The immunology and immunotherapy of breast cancer: an update

Adenocarcinomas of the breast behave clinically and epidemiologically in ways that show host resistance factors are important for outcome in addition to grade and stage of malignancy. Immune reactivity to autologous tumors is indicated by the general presence of lymphoid infiltration (LI) and regional lymph node changes; however, these changes predict favorable outcome only in non-metastatic disease. LI is characterized by CD4+ and CD8+ tumor infiltrating lymphocytes reflecting latent cell-mediated immunity (CMI). CMI and humoral immune reactivity have been demonstrated to autologous tumor and a variety of tumor-associated antigens (TAA) have been implicated including CEA, HER-2/neu, MAGE-1, p53, T/Tn and MUC-1. Immune incompetence involving CMI is progressive with the stage of breast cancer and is prognostically significant. Immunotherapy of several types has been designed to address this immunodeficiency and the TAAs involved. Animal models have employed drug therapy, cytokine transfection, vaccines with autologous tumor, cytokines like interferon alpha (IFN-alpha) and interleukin-2 (IL-2), TAA tumor vaccines, and immunotoxins with evidence of tumor regression by immunologic means. Immunotherapy of human breast cancer is a rapidly growing experimental area. Positive results have been obtained with natural IFN and interleukins, particularly in combination strategies (but not with high dose recombinant IFN or IL-2), with autologous tumor vaccine (but not yet with transfected autologous tumor); with a mucin carbohydrate vaccine (Theratope) in a combination strategy (but not with mucin core antigen) and with several immunotoxins. Combination strategies involving immunorestoration, contrasuppression, adjuvant, and immunotoxins are suggested for the future.

Down-Regulation of Tumoricidal NK and NK T Cell Activities by MHC Kb Molecules Expressed on Th2-Type γδ T and αβ T Cells Coinfiltrating in Early B16 Melanoma Lesions

We examined whether γδ T and αβ T cells accumulating in early B16 melanoma lesions regulate NK and NK T cells that attack tumor cells. Freshly isolated and cultured tumor-infiltrating lymphocyte (TIL) populations of NK and NK T cells lysed B16 and produced IFN-γ, whereas γδ T and a large part of αβ T cell populations had no substantial cytotoxicity against B16 and secreted Th2 cytokines. Furthermore, the freshly isolated NK1.1+ TIL population exhibited a higher anti-B16 effect than did splenocytes. γδ T and αβ T cell populations dramatically inhibited the cytotoxicity of NK and NK T cells in an MHC Kb-dependent manner. Culture supernatant from γδ T and αβ T cell populations inhibited the proliferation of NK and NK T cell populations but did not affect their cytotoxicity, suggesting that the released Th2 cytokines are merely partly involved in the down-modulation of NK-lineage cells. NK1.1+ cells obtained from TIL of γδ T cell-depleted mice significantly lysed B16 cells compared with those from control mice. Finally, anti-Kb Fab mAb injected intralesionally at an early, but not at a late, stage of development of B16 melanoma inhibited tumor growth. These findings suggest that Th2-type γδ T and αβ T cells infiltrating in early B16 development inhibit the tumoricidal activity of NK-lineage cells using their class I molecules and partly their suppressive cytokines.

Tumour-specific cytotoxic T lymphocyte activity in Th2-type Sézary syndrome: its enhancement by interferon-gamma (IFN-gamma) and IL-12 and fluctuations in association with disease activity

Sézary syndrome (SzS) is the leukaemic variant of cutaneous T cell lymphoma (CTCL), whose malignant T cells are of the Th2 type in most cases. In this study we investigated the tumouricidal activity of cytotoxic T lymphocytes (CTL) present in peripheral blood of a patient with Th2-type SzS, focusing on the effect of IL-2, IFN-gamma and IL-12 on their cytotoxic activity, and the relationship between their lytic capacity and the patient's clinical course. At four different time points during a 2-month clinical period, CD4+CD7- Sézary cells and CD8+ cells were separated from the patient's circulating cells. CD8+ cells were cultured with chemically attenuated, purified Sézary cells in the presence of IL-2 to develop specific cytotoxicity. The CD8+ cells thus cultured exhibited lytic activity against autologous Sézary cells. Concomitant addition of IFN-gamma or IL-12 exerted a synergistic cytolytic effect with IL-2 on the tumour cells. Cytotoxicity inhibition studies using MoAbs revealed that the cytotoxicity operated in MHC class I-, CD8- and alphabeta T cell receptor-dependent manners. Furthermore, eight CD8+ T cell clones generated from cultured CD8+ cells exhibited a strong cytotoxicity against Sézary cells in an MHC class I-restricted fashion. During the clinical course, the activity of generated CTL and the number of CD8+ cells were inversely correlated with disease activity as assessed by the serum level of lactate dehydrogenase. These findings suggest that CTL down-regulate the growth of malignant T cells in this long-standing disease. Since Th2 cytokines such as IL-4 down-modulate CTL activity, CTL are assumed to be usually suppressed in SzS, whose malignant T cells are of Th2 type. It is likely that the administration of IFN-gamma normalizes this Th2-skewing state, activates CTL, and thus exerts the therapeutic effectiveness in the treatment of CTCL.

Adoptively transferred EAE in gamma delta T cell-knockout mice

Recently there has been evidence suggesting that gamma delta receptor-bearing T cells may play a role in both multiple sclerosis (MS) and experimental allergic encephalomyelitis (EAE). We have recently described approaches for the generation of encephalitogenic T-cell populations from EAE-resistant strains of mice. Using encephalitogenic T-cell lines and clones generated from wild-type C57BL/6 mice we have studied adoptively transferred EAE in C57BL/6-TCR delta-knockout mice. We now report that the adoptive transfer of encephalitogenic T cells into TCR delta T-knockout mice leads to clinical EAE that is not significantly different in severity or time course than that seen after transfer into wild-type C57BL/6 mice. We conclude that gamma delta T cells do not play an integral role in the mediation or regulation of the effector-phase mechanisms in EAE.

Aerosol insulin induces regulatory CD8 gamma delta T cells that prevent murine insulin-dependent diabetes

Cellular immune hyporesponsiveness can be induced by the presentation of soluble protein antigens to mucosal surfaces. Most studies of mucosa-mediated tolerance have used the oral route of antigen delivery and few have examined autoantigens in natural models of autoimmune disease. Insulin is an autoantigen in humans and nonobese diabetic (NOD) mice with insulin-dependent diabetes mellitus (IDDM). When we administered insulin aerosol to NOD mice after the onset of subclinical disease, pancreatic islet pathology and diabetes incidence were both significantly reduced. Insulin-treated mice had increased circulating antibodies to insulin, absent splenocyte proliferation to the major epitope, insulin B chain amino acids 9-23, which was associated with increased IL-4 and particularly IL-10 secretion, and reduced proliferation to glutamic acid decarboxylase, another islet autoantigen. The ability of splenocytes from insulin-treated mice to suppress the adoptive transfer of diabetes to nondiabetic mice by T cells of diabetic mice was shown to be caused by small numbers of CD8 gamma delta T cells. These findings reveal a novel mechanism for suppressing cell-mediated autoimmune disease. Induction of regulatory CD8 gamma delta T cells by aerosol insulin is a therapeutic strategy with implications for the prevention of human IDDM.

Gamma delta T cells from tolerized alpha beta T cell receptor (TCR)-deficient mice inhibit contact sensitivity-effector T cells in vivo, and their interferon-gamma production in vitro

Contact sensitivity (CS) responses to reactive hapten Ag, such as picryl chloride (PCl) or oxazolone (OX), are classical examples of T cell-mediated immune responses in vivo that are clearly subject to multifaceted regulation. There is abundant evidence that downregulation of CS may be mediated by T cells exposed to high doses of Ag. This is termed high dose Ag tolerance. To clarify the T cell types that effect CS responses and mediate their downregulation, we have undertaken studies of CS in mice congenitally deficient in specific subsets of lymphocytes. The first such studies, using alpha beta T cell-deficient (TCR alpha -/-) mice, are presented here. The results clearly show that TCR alpha -/- mice cannot mount CS, implicating alpha beta T cells as the critical CS-effector cells. However, TCR alpha -/- mice can, after high dose tolerance, downregulate alpha +/+ CS-effector T cells adoptively transferred into them. By mixing ex vivo and then adoptive cell transfers in vivo, the active downregulatory cells in tolerized alpha -/- mice are shown to include gamma delta TCR+ cells that also can downregulate interferon-gamma production by the targeted CS-effector cells in vitro. Downregulation by gamma delta cells showed specificity for hapten, but was not restricted by the MHC. Together, these findings establish that gamma delta T cells cannot fulfill CS-effector functions performed by alpha beta T cells, but may fulfill an Ag-specific downregulatory role that may be directly comparable to reports of Ag-specific downregulation of IgE antibody responses by gamma delta T cells. Comparisons are likewise considered with downregulation by gamma delta T cells occurring in immune responses to pathogens, tumors, and allografts, and in systemic autoimmunity.

Protection against metastasis by immunization with an allogeneic lymphocyte antigen

Q5 antigens are expressed on the surface of various experimental murine tumor cells. They share partially common antigenicity with Qa-2 alloantigens expressed on normal lymphocytes. For that reason we tested the immunoprotection by anti-Qa-2 immunization of mice against a Q5+ tumor. Nerve fibrosarcoma (NSFA) tumor, which specifically develops metastasis in the lung, has been reported to be poorly immunogenic. However, expression of the Q5 antigen was evident on the surface of NFSA cells. After immunizing (C3H/He x B6.K1)F1 (Qa-2-) mice with B6 (Qa-2+) lymphocytes, the protection against the proliferation of the semi-syngeneic NFSA tumor was examined. First, immunization of normal mice induced resistance to NFSA cell transplants. Second, when the tumor cells were transplanted to the hind foot of a mouse and the resulting tumor was removed by amputating the leg, the mice were protected against the development of lung metastasis after immunization by intraperitoneal inoculation of B6 cells 3 days after tumor removal. Immunization with attenuated NFSA cells in this system failed to protect the mice from lung metastasis. On the other hand, inoculation of the mice with B6 cells without removal of the original tumor on the foot showed little effect on the progression of the tumor. Thus, cytotoxic T lymphocytes (CTL), which seemed to be present in an inactive form in the mice from which the tumor had not been removed, were induced in the mice after the removal of the major tumor followed by immunization with B6 lymphocytes. The induction of CTL by the immunization was suppressed in mice bearing large tumors. Cells stimulated by the tumor antigen seemed to be involved in the suppression. It was also shown that the Q5 antigen is the direct recognition target of the CTL since the activity of Q5-specific CTL clones in lysing tumor cells was inhibited by a monoclonal antibody specific for the Q5 antigen. In contrast to immunization with attenuated tumor cells, our novel allogeneic lymphocyte immunization procedure offers high CTL activation, by-passing the induction of T cell unresponsiveness.