Effector mechanisms in cyclosporine A-induced syngeneic graft-versus-host disease. Role of CD4+ and CD8+ T lymphocyte subsets

Syngeneic graft-versus-host disease (SGVHD) is a T cell-mediated autoimmune disease occurring postsyngeneic bone marrow transplantation and the administration of the potent immunosuppressive agent, cyclosporine A. Paradoxically, cyclosporine A disrupts the immunologic homeostasis governing self-tolerance. Our studies using an adoptive transfer model attempted to identify effector mechanisms associated with the autoimmune disease. Both CD4+ and CD8+ splenic T cells isolated from autoimmune donors were required for the adoptive transfer of active disease into lethally irradiated secondary recipients reconstituted with normal bone marrow. Doses of more than 5 x 10(6) of nylon wool depleted splenocytes from autoimmune donors effectively transferred disease into lethally irradiated secondary recipients. Splenocytes that are T cell depleted or CD4(+)-enriched cells did not elicit disease upon adoptive transfer. Nylon wool fractionated CD8+ splenocytes also failed to adoptively transfer disease unless high doses (greater than or equal to 30 x 10(6)) were used. The disease transferred with the CD8+ subset presented as acute type SGVHD and was self-limiting. The recombination of the individually isolated T cell subsets not only restored but also enhanced immune reactivity upon adoptive transfer. Moreover, use of the recombined subsets resulted in progressive disease with the development of chronic type SGVHD. The titration of each subset to the other suggested that a minimal number of CD4+ T cells was required to potentiate the CD8+ autoreactive cells in vivo. Further analysis of the helper cell involved demonstrated that it had a CD4+ CD45r- phenotype, characteristic of an amplifying helper cell population. Administration of IL-2 did not substitute for CD4+ Th cells but yet amplified the activity of unfractionated cells or recombined subsets implicating the role of other factors in the pathogenesis of SGVHD. Delineation of the effector mechanisms involved in SGVHD is critical in determining the underlying events that trigger either the production of autoreactive cells or the perturbation of the regulation of these autoreactive cells, culminating in autoimmunity.     

Characterization of RT6 bearing rat lymphocytes. I. Ontogeny of the RT6+ subset

The RT6 alloantigen is present on approximately 70% of peripheral T cells in the rat, but is absent from thymocytes and bone marrow lymphocytes. The results of further phenotypic analysis in the present study demonstrated that the RT6 alloantigen is expressed on approximately 45% of the helper/inducer (CD4; W3/25+) and 80% of the cytotoxic/suppressor (CD8; OX8+) peripheral T-cell subsets. Ontogenetic and thymus ablation studies indicated that the RT6+ T-cell subset is thymus-dependent and normally develops after the appearance of RT6-T cells in neonatal rats, and that the expression of RT6 is a post-thymic maturational event. Furthermore, intrathymic adoptive transfer of bone marrow cells demonstrated that RT6+ T cells are thymus-derived cells. These results show that most if not all RT6+ T cells are the progeny of RT6- T cells. However, they do not exclude the possibility that a separate lineage of RT6- T cells exists, which also has OX8+ and W3/25+ subsets. The possible developmental and functional relationships of RT6- and RT6+ T cells in the rat are discussed.     

Regulatory CD8+ T cells control neonatal tolerance to a Th2-mediated autoimmunity

Exposure of newborn animals to a foreign Ag may result in immunological tolerance to that specific Ag, a phenomenon called neonatal tolerance. We have previously reported that neonatal administration to Brown-Norway rats of mercury, a heavy metal toxicant, induces a dominant tolerance, specific for the chemical otherwise responsible for Th2 cell-mediated autoimmune responses in this susceptible strain of rats. Neonatal exposure to Ags can prime immunity, rather than inactivate or delete responses, and sustain regulatory functions effective against autoreactive T cells. Here, we address whether such a tolerant response is due to the generation of regulatory cells. The results suggest that the CD8(+) T cell subset is involved in neonatal tolerance to mercuric salt-induced Th2 autoimmune disease. Thus, we demonstrate that in vivo CD8 depletion breaks tolerance following mercury recall in animals under a neonatal tolerance protocol. Furthermore, adoptive cotransfer of splenocytes from naive and tolerant rats as well as transfer of CD8(+) T cells from tolerant animals prevent naive syngeneic rats from developing pathologic Th2 immune responses. These observations indicate that CD8(+) T cells are endowed with regulatory functions in neonatal tolerance and mediate active suppression. Moreover, neonatal tolerance induced the expansion of CD8(+)CD45RC(high) T cells and the emergence of a high percentage of IFN-gamma-synthesizing CD8(+) T cells, which probably reflects the implication of regulatory Tc1 cells. Thus, in vivo induction of neonatal tolerance suppresses Th2 autoimmune responses via generation of a CD8(+) cell-mediated regulatory response.     

T cell synergy in the primary MLR: proliferative kinetics, effector cell generation, and IL 2 production

A primary rat MLR was initiated, and on each of 8 consecutive days during the evolving culture, an aliquot of cells was separated into its constitutive helper/inducer (W3/25+) and suppressor/cytotoxic (OX8+) T cell subsets by a monoclonal antibody, Degalan-bead immunoadsorbent column technique. This allowed a detailed kinetic analysis of T cell proliferation, the generation of effector cells, and the production of IL 2 by each subset relative to net whole culture supernatant IL 2 activity. The primary MLR demonstrates an early period of helper/inducer cell proliferation, IL 2 production and accumulation, followed by a period of suppressor/cytotoxic cell (OX8+) proliferation and IL 2 consumption during which there are distinct waves of allospecific suppressor, followed by cytotoxic activity. If fresh T cells of the helper/inducer or suppressor/cytotoxic phenotype were preseparated and then cultured alone with irradiated allogeneic stimulator cells, proliferation was noted in both subsets despite no demonstrable IL 2 activity in cultures of the suppressor/cytotoxic cells. Finally, a suppressed primary MLR exhibited proliferative inhibition of both T cell subsets.     

Absence of the RT-6 T cell subset in diabetes-prone BB/W rats

Diabetes-prone Bio-breeding/Worcester (DP) rats exhibit a severe T cell lymphopenia and autoimmune pancreatic insulitis. The present results indicate that the T cell lymphopenia is due in large part, if not entirely, to the absence of the RT-6+ peripheral T cell subset, which includes members of both the helper/inducer (W3/25) and suppressor/cytotoxic (OX 8) antigenic phenotypes. Delineation of the causal mechanism(s) for the selective absence of RT-6+ T cells in DP rats may provide important insights into the cellular basis of the insulin-dependent diabetes mellitus syndrome in these animals.     

T cell regulation of the thymus-independent antibody response to trinitrophenylated-Brucella abortus (TNP-BA)

We have previously observed a reduction of the T cell-dependent primary antibody response to dinitrophenylated keyhole limpet hemocyanin, and an enhancement of the T cell-independent response to trinitrophenylated Brucella abortus (TNP-BA) in BALB/c mice after treatment with total lymphoid irradiation (TLI). To elucidate the relative contribution of T and B cells to the enhanced T cell-independent antibody responses after TLI, a syngeneic primary adoptive transfer system was utilized whereby irradiated hosts were reconstituted with unfractionated spleen cells or a combination of purified T and B cells from TLI-treated and untreated control mice. Antibody responses of purified splenic B cells from TLI-treated BALB/c mice (TLI/B) to TNP-BA were enhanced 10-fold as compared with those of unfractionated (UF) spleen cells or B cells from normal (NL) BALB/c mice (NL/UF and NL/B, respectively). Splenic T cells from normal animals (NL/T) suppressed the anti-TNP-BA response of TLI/B by more than 100-fold. NL/T neither suppressed nor enhanced the response of NL/B. On the other hand, T cells from TLI-treated mice (TLI/T) enhanced by 100-fold the anti-TNP-BA response of NL/B, but neither suppressed nor enhanced the response of TLI/B. Thus, T cells can regulate the "T cell-independent" antibody response to TNP-BA. However, experimental manipulation of the T and B cell populations is needed to demonstrate the regulatory functions.     

Mechanisms maintaining antibody-induced enhancement of allografts. II. Mediation of specific suppression by short lived CD4+ T cells

In DA rats grafted with PVG hearts, the injection of 1 ml of Wistar-Furth x DA)F1 anti-PVG serum on the day of grafting prevents rejection and induces a state of specific unresponsiveness. An adoptive transfer assay was used to test the capacity of T cell subsets, taken from rats given enhancing serum, to either restore rejection or to transfer unresponsiveness to syngeneic hosts irradiated with 9 Gy and grafted with donor (PVG) or third party (Wistar-Furth) hearts. W3/25+ (CD4+) cells from these animals retained some capacity to restore rejection until 50 days posttransplant, after which they invariably failed to restore PVG graft rejection but retained the capacity to effect Wistar-Furth rejection. At this time CD4+ cells were also capable of inhibiting naive but not specifically sensitized CD4+ cells capacity to restore PVG graft rejection in irradiated hosts. The development of CD4+ suppressor cells was concurrent with the appearance of clinically evident unresponsiveness in the host. MRC Ox8+ (CD8+) cells from enhanced rats when mixed with naive CD4+ cells delayed rejection in adoptive recipients but did not reestablish unresponsiveness. Paradoxically, the CD4+ cells that transfer unresponsiveness to the adoptive host proliferate such as normal cells in MLC to both donor and third party alloantigen. Unfractionated cells, CD4+ or CD8+ cells did not proliferate to relevant idiotype in vitro. The CD4+ cells after 3 days in culture, with either alloantigen or idiotype-bearing stimulator cells, lost their capacity to suppress in the adoptive transfer assay. The maintenance of specific unresponsiveness was thus shown to be due to a CD4+ suppressor T cell whose function was lost in culture, and therefore could not be detected in MLC or idiotype assays.     

Autoimmune effector cells. V.A monoclonal antibody specific for rat helper T lymphocytes inhibits adoptive transfer of autoimmune encephalomyelitis

The in vitro activation of spleen cells from donor rats immunized with myelin basic protein results in enhanced adoptive transfer of experimental allergic encephalomyelitis to syngeneic recipients. In this study, adoptive transfer was inhibited when monoclonal antibody W3/25, which defines an antigen on rat helper T lymphocytes, was included in the in vitro cultures. Partial inhibition was achieved with monoclonal antibody OX-3, which recognizes la antigen, whereas other anti-T cell monoclonal reagents were ineffective. These results support the conclusion that W3/25+T cells play an essential role in the induction of this autoimmune response.     

NK cell adoptive transfer combined with Ontak-mediated regulatory T cell elimination induces effective adaptive antitumor immune responses

Previous work from our laboratory showed that hydrocortisone (HC) combined with IL-15 induces expansion of activated human NK cells. We set up an experimental tumor model to evaluate the use of adoptively transferred, HC plus IL-15 (HC/IL-15)-activated and -expanded murine NK cells in the treatment of syngeneic mice carrying established lung metastases of the CT26 transplantable tumor. We also examined the effect of denileukin diftitox (Ontak) on the depletion of regulatory T cells to enhance the in vivo antitumor immunity induced by the adoptively transferred NK cells. Our results clearly demonstrate that murine DX5(+) NK cells are largely expanded in the presence of IL-15 plus HC while retaining intact their functional status. Moreover, when intravenously infused, they mediated significant antitumor responses against CT26 lung tumors in syngeneic BALB/c animals that were further enhanced upon pretreatment of the tumor-bearing animals with Ontak. Total splenocytes and isolated splenic T cells from NK-treated mice responded in vitro against CT26 tumor cells as evidenced by IFN-γ-based ELISPOT, proliferation, and cytotoxicity assays. Importantly, animals treated with Ontak plus adoptive transfer of HC/IL-15-expanded NK cells significantly retarded CT26 tumor growth after a rechallenge with the same tumor s.c. in their flanks. Taken altogether, our data suggest that NK cell adoptive transfer can trigger adaptive antitumor T cell responses, and regulatory T cell depletion by Ontak is mandatory for enabling HC/IL-15-activated NK cells to promote long-lasting adaptive antitumor immunity.     

Suppression of disease in New Zealand Black/New Zealand White lupus-prone mice by adoptive transfer of ex vivo expanded regulatory T cells

An increasing number of studies indicate that a subset of CD4(+) T cells with regulatory capacity (regulatory T cells; T(regs)) can function to control organ-specific autoimmune disease. To determine whether abnormalities of thymic-derived T(regs) play a role in systemic lupus erythematosus, we evaluated T(reg) prevalence and function in (New Zealand Black x New Zealand White)F(1) (B/W) lupus-prone mice. To explore the potential of T(regs) to suppress disease, we evaluated the effect of adoptive transfer of purified, ex vivo expanded thymic-derived T(regs) on the progression of renal disease. We found that although the prevalence of T(regs) is reduced in regional lymph nodes and spleen of prediseased B/W mice compared with age-matched non-autoimmune mice, these cells increase in number in older diseased mice. In addition, the ability of these cells to proliferate in vitro was comparable to those purified from non-autoimmune control animals. Purified CD4(+)CD25(+)CD62L(high) B/W T(regs) were expanded ex vivo 80-fold, resulting in cells with a stable suppressor phenotype. Adoptive transfer of these exogenously expanded cells reduced the rate at which mice developed renal disease; a second transfer after treated animals had developed proteinuria further slowed the progression of renal disease and significantly improved survival. These studies indicate that thymic-derived T(regs) may have a significant role in the control of autoimmunity in lupus-prone B/W mice, and augmentation of these cells may constitute a novel therapeutic approach for systemic lupus erythematosus.     

Cellular immunity in allograft rejection: role of lymphocyte subpopulations and T-cell subsets in rat cardiac allograft rejection

In this study, cellular requirements for rejection are examined by the use of adoptive transfer assays in the ACI to Lewis cardiac allograft model. The findings show that adoptive transfer of 1 x 10(8) spleen cells (SpL), 5 x 10(7) T-cells, and 2 x 10(7) helper T-cells (W3/25+) obtained from normal, nonsensitized donors restores acute ACI graft rejection in sublethally irradiated (750 rad) Lewis recipients. In contrast, reconstitution with 2 x 10(7) cytotoxic T-cells (0X8+) does not restore first-set graft rejection. Reconstitution of the irradiated recipients with either W3/25+ or 0X8+ T-cells obtained from specifically sensitized syngeneic donors resulted in acute rejection. The W3/25+ T-cell subset was significantly more potent (P less than 0.01) in effecting rejection on a per-cell basis. Adoptive transfer of SpL, T-cells, and 0X8+ T-cells obtained from sensitized rats led to accelerated cardiac allograft rejection in the naive secondary recipients while W3/25+ T-cells did not. This study suggests that although the W3/25+ T-cells alone have the capacity to initiate first-set graft rejection, both W3/25+ and 0X8+ subsets appear to be critical to the completion of rejection of heart allografts. We also examined the capacity of adoptively transferred B-cells from sensitized donors to influence graft rejection. Our findings suggest that while B-cells fail to restore the capacity for graft rejection in irradiated recipients, they can, however, present MHC antigens to the secondary naive host thus causing allosensitization which results in accelerated rejection of a subsequent graft.     

Cellular subsets involved in cell-mediated immunity to murine Plasmodium yoelii 17X malaria

Cell mediated immunity to nonlethal Plasmodium yoelli 17X (PY17X-NL) was examined in the CBA/CaJ mouse by adoptive transfer of sensitized T lymphocyte subsets. In intact mice, PY17X-NL causes a self-limiting infection with parasitemia levels ranging from 10 to 25% of total red blood cells. Upon recovery, mice are refractory to subsequent challenge with the homologous parasite. In T cell-depleted mice, PY17X-NL infections are extremely virulent and result in death of the host after parasitemia levels reach 50% or higher. The transfer of either Lyt-1 T cells or Lyt-2 T cells from immune animals into normal, naive animals produced accelerated recovery to subsequent infection. However, this adoptive transfer of immunity by either subset was dependent upon the presence of an I-J+, Lyt-null cell in the immune population. T cell deprivation precluded the ability of animals to control blood-stage infections. When T cell-depleted mice were reconstituted with naive, Ig-negative (T cell-enriched) spleen cells, parasitemia levels were controlled and the parasites were eliminated. When T cell-deprived animals were reconstituted with naive Lyt-1+2-, Ig-negative spleen cells, they experienced twofold higher parasitemias of longer duration than mice receiving unfractionated cells. Two of six of these Lyt-1 mice died of fulminant infections, suggesting that the presence of naive Lyt-2 cells enhances the degree of protection. Immune Lyt-2 T cells were highly protective in T cell-depleted animals. Protection by sensitized Lyt-1 T cells correlated with the induction of a monocytosis. On the other hand, protection by Lyt-2T cells occurred in the absence of monocytosis. The possibility that the immunity induced by each T cell subset is mediated by a different effector mechanism is discussed.     

T cell subsets mediating lethal graft versus host disease: demonstration that synergy between CD4+ and CD8+ T cells is the predominant mechanism in low responder rat strains

T cell subsets from rat strains that have been characterized as high and low responders to alloantigen were examined for their capacity to mediate lethal graft versus host disease (GVHD) across strain combinations incompatible for class I, class II, and non-MHC antigens. Inocula of 5 X 10(7) lymph node and spleen cells (LC) from low responder DA (RT1a) and high responder W/F (RT1u) strains caused lethal GVHD in (W/F X DA)F1 hybrids given 6 Gy whole body irradiation. W/F CD4+ (W3/25+) cells (2 X 10(7], equal to the number in 5 X 10(7) LC mediated lethal GVHD but 10(8) DA CD4+ cells were required to cause lethal GVHD. CD8+ (MRC OX8+) cells (5 X 10(7] from W/F rats alone caused lethal GVHD but those from DA rats could not. Mixtures of CD4+ and CD8+ DA T cells, equivalent to the number in 5 X 10(7) LC, did mediate lethal GVHD, demonstrating that synergy between the subsets was the predominant mechanism with DA cells. These results suggest that differences in alloreactivity between the strains tested may be due to alternate requirements for the alloactivation of T cell subsets; the high responder subsets being self-sufficient and the low responder subsets being dependent upon each other.     

CD8+ T lymphocytes protect SCID mice against Encephalitozoon cuniculi infection

Microsporidia are obligate intracellular parasites that cause opportunistic infections in immunocompromised patients. The role of two main T cell subsets in anti-microsporidial immunity has been studied using an Encephalitozoon cuniculi-severe combined immunodeficient (SCID) mouse model. Whereas SCID mice reconstituted with CD4+ T lymphocyte-depleted naive BALB/c splenocytes resolved the infection, adoptive transfer of CD8+ T cell-depleted splenocytes failed to protect the animals against a lethal E. cuniculi infection. Splenocytes from E. cuniculi-immune mice specifically killed syngeneic infected macrophages in a short-term 51Cr-release assay. These results suggest the crucial role of cytotoxic T lymphocytes in the protection against E. cuniculi infection.     

The immune response to Schistosoma mansoni infections in inbred rats. VI. Regulation by T cell subpopulations

These studies assess the roles of subpopulations of T lymphocytes in inducing and modulating resistance to Schistosoma mansoni. CDF rats were depleted of RT 7.1+ (anti-Pan-T), W3/25+ (anti-T helper/inducer), or OX8+ (anti-T suppressor) cells by the in vivo administration of monoclonal antibodies (mAb). The development of parasites and immunity to challenge by S. mansoni were compared with results in undepleted normal and congenitally athymic rats. Discrete subpopulations of T lymphocytes were adoptively transferred to ascertain effects upon parasite development and the protective immune response. In vitro studies, involving utilizing cocultivation of cell subpopulations +/- cyclosporin A, were utilized to dissect mechanisms. Depletion of T lymphocytes by anti-RT7.1 mAb and anti-W3/25 mAb resulted in augmented initial worm development, suboptimal resistance, and decreased antibody and delayed-type hypersensitive reactivity directed against schistosome antigens. Depletion with OX8 mAb produced opposite effects. The adoptive transfer of T cell subpopulations produced concordant results with T cell regulation expressed B cell-dependent effector mechanisms. The coadoptive transfer of cells resulted in the suppression of resistance afforded by the W3/25+ cells by OX8+ cells, which could be augmented in vitro by cyclosporin A. Thus, protective immunity to S. mansoni in rats is regulated by discrete subpopulations of T lymphocytes. The findings suggest the possibility of selective immune regulation of resistance based on the manipulation of specific T cell subpopulation.     

Accumulation of CD4+ T cells in the colon of CsA-treated mice following myeloablative conditioning and bone marrow transplantation

Syngeneic graft vs. host disease (SGVHD) was first described as a graft vs. host disease-like syndrome that developed in rats following syngeneic bone marrow transplantation (BMT) and cyclosporin A (CsA) treatment. SGVHD can be induced by reconstitution of lethally irradiated mice with syngeneic bone marrow cells followed by 21 days of treatment with the immunosuppressive agent CsA. Clinical symptoms of the disease appear 2-3 wk following cessation of CsA therapy, and disease-associated inflammation occurs primarily in the colon and liver. CD4(+) T cells have been shown to play an important role in the inflammatory response observed in the gut of SGVHD mice. Time-course studies revealed a significant increase in migration of CD4(+) T cells into the colon during CsA therapy, as well as significantly elevated mRNA levels of TNF-α, proinflammatory chemokines, and cell adhesion molecules in colonic tissue of CsA-treated animals compared with BMT controls, as early as day 14 post-BMT. Homing studies revealed a greater migration of labeled CD4(+) T cells into the gut of CsA-treated mice at day 21 post-BMT than control animals via CsA-induced upregulation of mucosal addressin cell adhesion molecule. This study demonstrates that, during the 21 days of immunosuppressive therapy, functional mechanisms are in place that result in increased homing of CD4(+) T effector cells to colons of CsA-treated mice.     

Murine syngeneic graft-versus-host disease is responsive to broad-spectrum antibiotic therapy

Murine syngeneic graft-versus-host disease (SGVHD) initiates colon and liver inflammation following lethal irradiation, reconstitution with syngeneic bone marrow transplantation, and therapy with the immunosuppressive agent cyclosporine A. Previous studies have demonstrated that the inducible disease is mediated by CD4(+) T cells with increased reactivity of peripheral and liver-associated lymphocytes against intestinal microbial Ags. In the current report, studies were performed to analyze the specificity of the CD4(+) T cell response of T cells isolated from diseased animals and to determine the in vivo role of the microbiota to the development of SGVHD. Increased major histocompatibility Ag (MHC) class II-restricted responsiveness of SGVHD CD4(+) T cells against microbial Ags isolated from the ceca of normal animals was observed. The enhanced proliferative response was observed in the CD62L(-) memory population of CD4(+) T cells. To determine the role of the bacterial microbiota in the development of murine SGVHD, control and CsA-treated bone marrow transplantation animals were treated with broad-spectrum antibiotics (metronidazole, ciprofloxacin) after transplantation. Cyclosporine A-treated animals that were given antibiotic therapy failed to develop clinical symptoms and pathological lesions in the target tissues characteristic of SGVHD. Furthermore, the reduction in intestinal bacteria resulted in the elimination of the enhanced antimicrobial CD4(+) T cell response and significantly reduced levels of the inflammatory cytokines, IFN-γ, IL-17, and TNF-α. The elimination of the disease-associated inflammatory immune responses and pathology by treatment with broad-spectrum antibiotics definitively links the role of the microbiota and microbial-specific immunity to the development of murine SGVHD.     

Effect of the joint use of BCG and antithymocyte serum on the growth of a syngeneic tumor in mice

The growth of the syngeneic tumor Acatol in BALB/c mice was retarded if the animals were pretreated with BCG or antilymphocyte serum (ATS). Combined use of BCG and ATS led to a significantly more powerful retardation as compared to the effect produced by each factor alone. Using the adoptive transfer of splenocytes from treated mice it was shown that tumor growth suppression is effected by the cell types other than T lymphocytes and macrophages. It is probable that the effector cells within the given system are K cells and natural killer cells. The results attest to a possibility of search for a two-directional action on the immune system of the tumor host, which would stimulate antitumor effector cells and inhibit the activity of suppressors, particularly that of T suppressors.     

Endogenous H/K ATPase beta-subunit promotes T cell tolerance to the immunodominant gastritogenic determinant

A CD4(+) T cell response to the gastric H/K ATPase beta-subunit (H/Kbeta) is required for the onset of experimental autoimmune gastritis in BALB/c mice. The extent to which endogenous H/Kbeta contributes toward the tolerance of the H/Kbeta-specific T cell repertoire in normal individuals is not known. By comparison of T cell responses in H/Kbeta-deficient (o/o) and H/Kbeta-expressing BALB/c mice, in this work we show that the endogenous H/Kbeta autoantigen plays a major role in the tolerance of pathogenic H/Kbeta-specific T cells. First, T cell-dependent Ab responses to the H/Kbeta Ag were enhanced in H/K ATPase-immunized H/Kbeta-deficient mice compared with wild-type mice. Second, peptide immunization experiments indicated that immune responses to the major gastritogenic epitope of the H/K ATPase, namely H/Kbeta(253-277), were significantly more vigorous in H/Kbeta-deficient mice compared with wild-type mice. Third, unfractionated splenocytes from H/Kbeta-deficient mice, but not H/Kbeta-expressing mice, induced autoimmune gastritis after adoptive transfer to BALB/c nude mice. The enhanced responses to H/Kbeta in H/Kbeta-deficient mice were shown to be intrinsic to CD4(+)CD25(-) T cells rather than a change in status of CD4(+)CD25(+) regulatory T cells. We conclude from these studies that the H/Kbeta-specific T cells in wild-type mice represent the residue of a T cell repertoire, directed toward a single determinant, that has been subjected to partial tolerance induction.     

Tolerance mechanism in experimental ovarian and gastric autoimmune diseases.

Neonatal splenocytes, neonatal thymocytes, or phenotypically mature adult thymocytes, transferred from normal BALB/c mice to syngeneic athymic nu/nu (or SCID) mice, led to autoimmune oophoritis and autoimmune gastritis, with corresponding serum autoantibodies, in the recipients. The overall disease incidence was 73%; the pathology ranged from mild to severe, with complete loss of ovarian follicles and gastric parietal cells. CD4+ neonatal spleen cells and CD4+ CD8- adult thymocytes were required for autoimmune disease induction. Adult spleen cells did not elicit disease, but they prevented disease when co-transferred with neonatal spleen cells. However, in confirmation of an earlier report by Sakaguchi et al., (J. Exp. Med. 161:72, 1985), a subset of adult splenic T cells expressing a low level of CD5 molecules elicited similar autoimmune diseases. Thus, self-reactive T cells responsible for autoimmune disease of the stomach and ovary are not effectively deleted in the thymus, and they exist in the peripheral lymphoid organs of normal mice. We conclude that the functional expression of the self-reactive T cells is ontogenetically regulated; whereas T cells in the neonatal mice readily elicited autoimmune diseases in nu/nu recipients, regulatory cells may render self-reactive T cells in the normal adults unresponsive.