Autoimmune ovarian inflammation triggered by proinflammatory (Th1) T cells is compatible with normal ovarian function in mice.

The detection of noninfectious ovarian inflammation (oophoritis) and serum ovarian autoantibodies in a patient with premature ovarian failure is indicative of an autoimmune etiology. The mechanisms of autoimmune ovarian injury leading to loss of function are currently unknown. In this study we investigated the impact of oophoritis on ovarian function based on two murine autoimmune ovarian disease (AOD) models. AOD can be induced by thymectomy at Day 3 after birth (d3tx). D3tx mice develop ovarian inflammation and atrophy with loss of oocytes. In these mice, ovarian atrophy and not oophoritis correlated with abnormal estrous cyclicity. The second AOD model is induced by active immunization of adult mice with a murine ZP3 peptide (pZP3) in adjuvant. After active immunization, the zona pellucida antibody titer, not oophoritis, correlated with reduced fertility. To investigate the effect of oophoritis in the absence of antibody response or ovarian atrophy, pZP3-specific T cells were passively transferred into naive syngeneic mice. This recruited cytokine-producing cells into the ovaries so that elevated cytokine production and its effect on ovarian function could be examined. Recipients of pZP3-specific T cells developed severe granulomatous oophoritis, and the diseased ovaries had elevated ovarian mRNA levels of interferon-gamma, interleukin-1beta, and tumor necrosis factor alpha. Despite these changes, fertility rates and gonadotropin-induced follicular development remained essentially normal. Therefore, normal ovarian function is compatible with severe ovarian inflammation mediated by autoreactive T cells.     

Cutting edge: Autoimmune disease in day 3 thymectomized mice is actively controlled by endogenous disease-specific regulatory T cells

Female B6AF1 mice thymectomized on day 3 (d3tx) develop autoimmune ovarian disease (AOD) and dacryoadenitis. It has been hypothesized that d3tx breaks tolerance by depleting late ontogeny regulatory T cells (Treg). We now report that Treg greatly expand over effector T cells in d3tx mice and adoptively suppress autoimmune disease in d3tx recipients. In the d3tx donors, Treg from ovarian lymph nodes (LN) preferentially suppress AOD and Treg from lacrimal gland LN preferentially suppress dacryoadenitis, suggesting they are strategically positioned for disease control. Indeed, the autologous disease in d3tx mice is dramatically enhanced by in vivo depletion of endogenous Treg. Moreover, normal 3-day-old mice possess Treg that suppress AOD and autoimmune gastritis as efficiently as adult cells. Thus, d3tx mice possess disease-relevant Treg of presumed neonatal origin. They accumulate in the regional LN and actively inhibit concurrent autoimmune disease; however, they cannot fully prevent autoimmune disease development.     

CD40 ligand in pathogenesis of autoimmune ovarian disease of day 3-thymectomized mice: implication for CD40 ligand antibody therapy

The blockade of CD40 ligand (CD40L) is effective in autoimmune disease prevention. Recently, a brief period of CD40L mAb treatment was reported to induce tolerance and enhancement of CD4(+)CD25(+) regulatory T cell activity. We therefore determined the efficacy of CD40L mAb treatment in autoimmunity that resulted from CD4(+)CD25(+) regulatory T cell deficiency. Autoimmune ovarian disease (AOD) and oocyte autoantibody response of day 3-thymectomized (d3tx) mice were inhibited by continuous CD40L mAb treatment from day 3, or from days 10-14, whereas CD40L mAb treatment confined to the neonatal week was ineffective. The enhanced expression of memory markers (CD44 and CD62L(low)) on CD4(+) T cells of the d3tx mice was unaffected by CD40L mAb treatment. In contrast, their increased T cell activation markers (CD69 and CD25) were eliminated by CD40L mAb treatment. Moreover, ex vivo activated T cells of d3tx mice expressed elevated intracellular IFN-gamma, and this was also blocked by CD40L mAb. The memory T cells, although nonpathogenic in CD40L mAb-positive environment, transferred severe AOD to CD40L mAb(-) neonatal recipients. Most importantly, CD40L mAb treatment inhibited AOD in recipients of T cells from d3tx donors with severe AOD and led to regression of AOD in d3tx mice documented at 4 wk. Therefore, 1) the continuous presence of CD40L mAb both prevents and causes regression of AOD in the d3tx mice; and 2) the multiple steps of the d3tx autoimmune disease, including T cell activation, cytokine production, T cell-mediated inflammation, and tissue injury, are CD40L dependent.     

Effector and regulatory cells in autoimmune oophoritis elicited by neonatal thymectomy.

(C57BL/6 x A/J)F1 (B6AF1) mice thymectomized between days 1 and 4 of age develop autoimmune oophoritis (D3TX oophoritis) 4 to 6 wk later. Oophoritis can be adoptively transferred to young recipients, and the disease in D3TX mice is prevented by reconstitution with normal adult spleen cells. The present study was further defined the nature of the effector and suppressor cells. Contrary to an earlier report, oophoritis is transferred to syngeneic and not allogeneic recipients. The spleen cells from D3TX mice when stimulated in vitro with Con A, also transfer oophoritis to adult recipients. The effector cells are CD4+: oophoritis transfer is abrogated by CD4 antibody and not by CD8 antibody and C. Spleen cells from D3TX male mice transfer disease less efficiently than female cells, thus endogenous ovarian Ag may be required for activation of effector T cells. T cells from normal adult spleen that suppress D3TX oophoritis also appear to be of CD4+ phenotype. These cells are likely to be derived from adult thymus because adult thymocytes also suppress D3TX disease. We were unable to substantiate the earlier claim that suppressor cells in normal mice are ovarian Ag specific. Thus male and female spleen cells suppress disease with comparable efficiency, and deprivation of endogenous ovarian Ag by neonatal ovariectomy of cell donors had no observable effect on disease suppression.     

The postnatal maternal environment affects autoimmune disease susceptibility in A/J mice

The postnatal maternal environment is known to increase susceptibility to a number of autoimmune diseases. Here we asked whether the postnatal maternal environment could influence autoimmune disease development to day 3 thymectomy (d3tx)-induced autoimmune ovarian disease (AOD) and experimental allergic encephalomyelitis (EAE) in cross-fostered A/J and B6 mice. A/J pups foster-nursed by B6 mothers exhibit an increase in autoimmune disease development while cross-fostering B6 pups on A/J mothers did not alter their susceptibility. The increase in AOD incidence seen in foster-nursed d3tx A/J mice correlated with a decrease in the total number of CD4⁺ T cells in the lymph nodes of these animals. Analysis of the cellular composition in the milk revealed that B6 mice shed significantly more maternally derived lymphocytes into their milk compared to A/J mothers. These data suggest that there are maternally derived postnatal factors that influence the development of autoimmune disease in A/J mice.     

Aod1 controlling day 3 thymectomy-induced autoimmune ovarian dysgenesis in mice encompasses two linked quantitative trait loci with opposing allelic effects on disease susceptibility

Day 3 thymectomy (D3Tx) leads to a paucity of CD4(+)CD25(+) suppressor T cells, a loss of peripheral tolerance, and the development of organ-specific autoimmune disease in adult mice. Importantly, D3Tx does not lead to autoimmune disease in all mouse strains, indicating that this process is genetically controlled. Previously, we reported linkage of D3Tx-induced autoimmune ovarian dysgenesis (AOD) and its intermediate phenotypes, antiovarian autoantibody responsiveness, oophoritis, and atrophy, to five quantitative trait loci (QTL), designated Aod1 through Aod5. We also showed interaction between these QTL and H2 as well as Gasa2, a QTL controlling susceptibility to D3Tx-induced autoimmune gastritis. To physically map Aod1, interval-specific bidirectional recombinant congenic strains of mice were generated and studied for susceptibility to D3Tx-induced AOD. Congenic mapping studies revealed that Aod1 controls susceptibility to oophoritis and comprises two linked QTL with opposing allelic effects. Aod1a resides between D16Mit211 (23.3 cM) and D16Mit51 (66.75 cM) on chromosome 16. Aod1b maps proximal of Aod1a between D16Mit89 (20.9 cM) and D16Mit211 (23.3 cM) and includes the candidate genes stefin A1, A2, and A3 (Stfa1-Stfa3), inhibitors of cathepsin S, a cysteine protease required for autoantigen presentation, and the development of autoimmune disease of the salivary and lacrimal glands following D3Tx. cDNA sequencing revealed the existence of structural polymorphisms for both Stfa1 and Stfa2. Given the roles of cathepsins in Ag processing and presentation, Stfa1 and Stfa2 alleles have the potential to control susceptibility to autoimmune disease at the level of both CD4(+)CD25(+) suppressor and CD4(+)CD25(-) effector T cells.     

Maternal autoantibody triggers de novo T cell-mediated neonatal autoimmune disease

Although human maternal autoantibodies may transfer transient manifestation of autoimmune disease to their progeny, some neonatal autoimmune diseases can progress, leading to the loss of tissue structure and function. In this study we document that murine maternal autoantibody transmitted to progeny can trigger de novo neonatal pathogenic autoreactive T cell response and T cell-mediated organ-specific autoimmune disease. Autoantibody to a zona pellucida 3 (ZP3) epitope was found to induce autoimmune ovarian disease (AOD) and premature ovarian failure in neonatal, but not adult, mice. Neonatal AOD did not occur in T cell-deficient pups, and the ovarian pathology was transferable by CD4(+) T cells from diseased donors. Interestingly, neonatal AOD occurred only in pups exposed to ZP3 autoantibody from neonatal days 1-5, but not from day 7 or day 9. The disease susceptibility neonatal time window was not related to a propensity of neonatal ovaries to autoimmune inflammation, and it was not affected by infusion of functional adult CD4(+)CD25(+) T cells. However, resistance to neonatal AOD in 9-day-old mice was abrogated by CD4(+)CD25(+) T cell depletion. Finally, neonatal AOD was blocked by Ab to IgG-FcR, and interestingly, the disease was not elicited by autoantibody to a second, independent native ZP3 B cell epitope. Therefore, a new mechanism of neonatal autoimmunity is presented in which epitope-specific autoantibody stimulates de novo autoimmune pathogenic CD4(+) T cell response.     

Requirements of NK cells and proinflammatory cytokines in T cell-dependent neonatal autoimmune ovarian disease triggered by immune complex

A model of neonatal autoimmune disease has been described recently in which an epitope-specific autoantibody to murine zona pellucida 3 induces severe ovarian disease in neonatal, but not adult, mice (neonatal AOD). The autoantibody forms immune complex with endogenous ovarian zona pellucida 3, and a pathogenic CD4(+) T cell response is triggered. The basis for the predominant neonatal susceptibility has not been clarified. In this study innate immunity, including neonatal NK cells, in neonatal AOD was investigated. Neonatal spleen contained readily detectable NK1.1(+)TCRVbeta(-), but not NK1.1(+)TCRVbeta(+), cells. Ab depletion of NK1.1(+)TCRVbeta(-) cells inhibited neonatal AOD development. Moreover, in adoptive transfer of neonatal AOD, recipient disease was ameliorated when either donor or recipient NK cells were depleted. Thus, NK cells operate in both induction and effector phases of the disease. IFN-gamma was produced by neonatal NK cells in vivo, and it may be important in neonatal AOD. Indeed, ovaries with neonatal AOD expressed high levels of IFN-gamma and TNF-alpha which correlated with disease severity, and the disease was inhibited by IFN-gamma or TNF-alpha Ab. Importantly, disease was enhanced by recombinant IFN-gamma, and treatment of T cell donors with IFN-gamma Ab also significantly reduced adoptive transfer of neonatal AOD. Finally, neonatal AOD was ameliorated in mice deficient in FcgammaRIII and was enhanced in FcgammaRIIB-deficient mice. We conclude that neonatal NK cells promote pathogenic T cell response at multiple stages during neonatal autoimmune disease pathogenesis. Also operative in neonatal AOD are other mediators of the innate system, including proinflammatory cytokines and FcgammaRIII signaling.     

Organ-specific autoimmune disease induced in mice by elimination of T cell subsets. V. Neonatal administration of cyclosporin A causes autoimmune disease

Cyclosporin A (CsA), a potent immunosuppressive drug, caused organ-specific autoimmune disease, such as gastritis with anti-parietal cell autoantibodies or oophoritis with anti-oocyte autoantibodies, in BALB/c mice when the drug was administered daily for 1 wk to newborns. Administration to adult mice did not. CsA abrogated the production of L3T4+ T cells and Lyt-2+ T cells in the thymus. Consequently, these T cells were substantially depleted from the peripheral lymphoid organs, especially when the drug was administered from the day of birth. Autoimmune disease was prevented when CsA-treated newborn mice were inoculated with splenic T cells from normal syngeneic mice. However, removal of the thymus immediately after neonatal CsA treatment produced autoimmune disease with a higher incidence and in a wider spectrum of organs, i.e., thyroiditis, sialoadenitis of the salivary gland, gastritis, insulitis of the endocrine pancreas, adrenalitis, oophoritis, or orchitis. Each autoimmune disease was accompanied by the development of circulating autoantibodies specific for the corresponding organ Ag. Immunopathology of these autoimmune diseases was quite similar to that of human organ-specific autoimmune diseases.     

Failure of CD25+ T cells from lupus-prone mice to suppress lupus glomerulonephritis and sialoadenitis

The development of organ-specific autoimmune diseases in mice thymectomized on day 3 of life (d3tx mice) can be prevented by transferring CD4(+)CD25(+) T cells from syngeneic, normal adult mice. Using a d3tx model, we asked whether CD4(+)CD25(+) T cell deficiency contributes to glomerulonephritis (GN) in lupus-prone mice. New Zealand Mixed 2328 (NZM2328) mice spontaneously develop autoantibodies to dsDNA and female-dominant, fatal GN. After d3tx, both male and female NZM2328 mice developed 1) accelerated dsDNA autoantibody response, 2) early onset and severe proliferative GN with massive mesangial immune complexes, and 3) autoimmune disease of the thyroid, lacrimal gland, and salivary gland. The d3tx male mice also developed autoimmune prostatitis. The transfer of CD25(+) cells from 6-wk-old asymptomatic NZM2328 donors effectively suppressed dsDNA autoantibody and the development of autoimmune diseases, with the exception of proliferative lupus GN and sialoadenitis. This finding indicates that NZM2328 lupus mice have a selective deficiency in T cells that regulates the development of lupus GN and sialoadenitis. After d3tx, the proliferative GN of female mice progressed to fatal GN, but largely regressed in the male, thereby revealing a checkpoint in lupus GN progression that depends on gender.     

Immunization with recombinant murine cytomegalovirus expressing murine zona pellucida 3 causes permanent infertility in BALB/c mice due to follicle depletion and ovulation failure

Zona pellucida (ZP) glycoproteins are promising candidate antigens for use in immunocontraceptive vaccines because of their crucial role in mammalian fertilization. A single intraperitoneal immunization with recombinant murine cytomegalovirus engineered to express murine ZP3 (rMCMV-mZP3) induces permanent infertility with no evident systemic illness in female BALB/c mice. To investigate the mechanisms underpinning reproductive failure elicited by rMCMV-mZP3, ovarian parameters and reproductive function were evaluated at time points spanning 10 days to 5 wk after virus inoculation. Fertility was substantially impaired by 14 days after inoculation with rMCMV-mZP3 and was fully ablated by 21 days. Pregnancies established after inoculation but before complete infertility showed no adverse effects on fetal viability assessed at Day 17.5 post coitum (pc). Infertile mice retained estrous cycling activity and remained receptive to mating; however, at Day 3.5 pc there were fewer developing embryos and corpora lutea, plasma progesterone content was reduced, and there was no evidence of excess unfertilized oocytes. Consistent with this, profound ovarian pathology was evident from 10 days after rMCMV-mZP3 inoculation, with a decline first in mature ovarian follicles and then in immature ovarian follicles and with diminished expression of genes regulating follicle development, including Nobox, Gdf9, and Gja1 (connexin43). Follicle loss was associated with mild focal oophoritis and with recruitment of inflammatory leukocytes, predominantly CD4(+) and CD8(+) T cells evident from 10 days after virus inoculation. These data indicate that vaccination with rMCMV-mZP3 causes permanent infertility in BALB/c mice principally due to induction of ovarian autoimmune pathology leading to progressive oocyte depletion and eventual ovulation failure.     

Persistence of physiological self antigen is required for the regulation of self tolerance

Endogenous Ag requirement for induction and maintenance of T cell tolerance has been extensively investigated in mice that express a transgenic Ag and/or its cognate transgenic TCR. In contrast, studies on tolerance for physiologically expressed self Ag and normal T cells are limited. Herein, we showed that the murine ovarian-specific ZP3 Ag is detectable from birth. Tolerance to ZP3 is detected in female relative to male mice. In comparison to males, 100-fold more ovarian peptide (pZP3) is required to elicit a comparable pathogenic response in females. Female tolerance to pZP3 was dependent on the presence of endogenous ovarian Ag, because neonatal ovariectomy converted the female response to that of males. Moreover, in female mice that were ovariectomized from the ages of 1-6 wk, the pZP3 responses were enhanced to the male level if ovaries were removed up to 7 days, but not 3 days, before adult challenge with pZP3. Thus, the physiologically expressed ZP3 Ag induces tolerance to pZP3, and the maintenance of tolerance is critically dependent on the continuous presence of the endogenous ovarian Ag. In contrast, exposure to endogenous ovarian Ag confined to the neonatal period is insufficient for the induction and maintenance of tolerance to ZP3.     

Autoimmune targeted disruption of the pituitary-ovarian axis causes premature ovarian failure

Premature ovarian failure (POF) is characterized by amenorrhea and high serum levels of follicle-stimulating hormone (FSH). POF causes female infertility and represents a substantial women's health risk affecting 1% of women by age 40. Although ovarian autoimmunity has been associated with POF, the identity of ovarian Ags recognized is unknown. In this study, we show that autoimmune-targeted disruption of the pituitary-ovarian axis leads to POF. Immunization of SWXJ female mice with the p215-234 peptide derived from mouse inhibin-alpha activates CD4(+) T cells and induces experimental autoimmune oophoritis with a unique biphasic phenotype characterized by an early stage of enhanced fertility followed by a delayed stage of POF. Affected mice show high serum levels of inhibin-alpha-neutralizing Abs that prevent inhibin-mediated down-regulation of activin-induced pituitary FSH release. The loss of activin/FSH down-regulation leads to prolonged metestrus-diestrus, superovulation, increased numbers of mature follicles, increased offspring, accelerated depletion of primordial follicles, and ultimately premature infertility. Thus, inhibin-alpha-targeted experimental autoimmune oophoritis is initiated by CD4(+) Th1 T cells that stimulate B cells to produce inhibin-alpha-neutralizing Abs directly capable of mediating POF and transferring disease into naive recipients. Our inhibin-alpha autoimmune model of POF shows how premature infertility may develop in the context of elevated FSH levels thereby closely mimicking the hallmark features of human POF.     

Retargeting T cell-mediated inflammation: a new perspective on autoantibody action

To understand the pathogenesis of organ-specific autoimmune disease requires an appreciation of how the T cell-mediated inflammation is targeted, and how the organ function is compromised. In this study, autoantibody was documented to influence both of these parameters by modulating the distribution of T cell-mediated inflammation. The murine autoimmune ovarian disease is induced by immunization with the ZP3330-342 peptide of the ovarian zona pellucida 3 glycoprotein, ZP3. Passively transferred or actively induced Ab to ZP3335-342 bound to the zona pellucida in the functional and degenerative ovarian follicles, and the ovaries remained histologically normal. Transfer of ZP3330-342 peptide-specific T cells targeted the degenerative follicles and spared the functional follicles, and the resultant interstitial oophoritis was associated with unimpaired ovarian function. Unexpectedly, the coexistence of ZP3330-342 peptide-specific T cells and zona-bound autoantibody led to a dramatic translocation of the ovarian inflammation to the growing and mature ovarian follicles, with destruction of the ovarian functional unit. Ab retargeted both Th1-induced mononuclear inflammation and Th2-induced eosinophilic inflammation, and retargeting was induced by murine and rat polyclonal Abs to multiple distinct native B cell determinants of the zona pellucida. Therefore, by reacting with the native determinants in tissue Ag, Ab alters the distribution of T cell-mediated inflammation, and results in destruction of the functional units of the target organ. We propose that this is a clinically important and previously unappreciated element of Ab action in autoimmune disease.     

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.     

Development of murine lupus in CD4-depleted NZB/NZW mice. Sustained inhibition of residual CD4+ T cells is required to suppress autoimmunity.

Chronic administration of anti-CD4 mAb prevents autoimmune disease in NZB/NZW F1 (B/W) mice. This may be due either to CD4 cell depletion or to inhibition of CD4 cell function. To evaluate the relative importance of these mechanisms, we devised a system in which the consequences of cell depletion could be analyzed independent of the inhibitory effects of chronic mAb therapy. This was accomplished by performing adult thymectomy before mAb administration. Specifically, female B/W mice underwent thymectomy or sham thymectomy at age 6 wk, followed at age 3 mo by a short course of either anti-CD4 (2 mg/wk for 3 wk) or saline. Treatment with anti-CD4 depleted 90% of circulating CD4 cells, but a small subpopulation (10%) of CD4 cells was refractory to depletion. In non-thymectomized mice, the CD4 population gradually reconstituted after cessation of therapy. In contrast, in thymectomized mice, recovery of CD4 cells was prevented by the absence of the thymus. Despite the striking reduction in CD4 cells in thymectomized mice, severe autoimmune disease developed, with autoantibody levels, proteinuria, and mortality comparable with non-thymectomized, nondepleted controls. The unexpected development of lupus nephritis in thymectomized, CD4-depleted B/W mice suggested that the thymus might be required to achieve the benefits of therapy with anti-CD4. To exclude this possibility, we demonstrated that chronic therapy with anti-CD4 prevents autoimmunity in thymectomized B/W mice. These findings imply that: 1) substantial depletion of CD4 T cells is not sufficient to suppress autoimmunity; 2) suppression of autoimmunity requires sustained functional inhibition of CD4 T cells; and 3) a small subpopulation of CD4 cells that is refractory to depletion by anti-CD4 is sufficient to promote the full expression of murine lupus in B/W mice.     

Critical involvement of OX40 ligand signals in the T cell priming events during experimental autoimmune encephalomyelitis

OX40 ligand (OX40L) expressed on APCs, and its receptor, OX40 present on activated T cells, are members of the TNF/TNFR family, respectively, and have been located at the sites of inflammatory conditions. We have observed in OX40L-deficient mice (OX40L(-/-)) an impaired APC capacity and in our recently constructed transgenic mice expressing OX40L (OX40L-Tg), a markedly enhanced T cell response to protein Ags. Using these mice, we demonstrate here the critical involvement of the OX40L-OX40 interaction during the T cell priming events in the occurrence of experimental autoimmune encephalomyelitis (EAE). In OX40L(-/-) mice, abortive T cell priming greatly reduced the clinical manifestations of actively induced EAE, coupled with a reduction in IFN-gamma, IL-2, and IL-6 production in vitro. Adoptive transfer experiments however revealed an efficient transfer of disease to OX40L(-/-) mice using wild-type donor T cells, indicating an intact capacity of OX40L(-/-) mice to initiate effector responses. On the other hand, OX40L(-/-) donor T cells failed to transfer disease to wild-type recipient mice. Furthermore, OX40L-Tg mice developed a greater severity of EAE despite a delayed onset, while both OX40L-Tg/CD28(-/-) and OX40L-Tg/CD40(-/-) mice failed to develop EAE demonstrating a requisite for these molecules. These findings indicate a pivotal role played by OX40L in the pathogenesis of EAE.     

Paradoxical dampening of anti-islet self-reactivity but promotion of diabetes by OX40 ligand

Costimulatory signals received by diabetogenic T cells during priming by or upon secondary encounter with autoantigen are decisive in determining the outcome of autoimmune attack. The OX40-OX40 ligand (OX40L) costimulatory pathway is known to influence T cell responses, prompting us to examine its role in autoimmune diabetes. A null allele at OX40L completely prevented diabetes development in nonobese diabetic mice and strongly reduced its incidence in a TCR transgenic model (BDC2.5). However, somewhat paradoxically, the initial activation of T cells responsive to islet beta cell Ag was slightly faster and more efficient in the absence of OX40L, with an increased degree of cell proliferation and survival in the deficient hosts. Activated T cell migration into and retention within the islets was also slightly accelerated. When challenged in vitro, splenocytes from BDC2.5.OX40L(o/o) mice showed no altered reactivity to exogenously added peptide, no bias to the Th1 or Th2 phenotype, and no alteration in T cell survival. Thus, the OX40/OX40L axis has the paradoxical effect of dampening the early activation and migration of autoimmune T cells, but sustains the long-term progression to autoimmune destruction.     

Danger and OX40 receptor signaling synergize to enhance memory T cell survival by inhibiting peripheral deletion

This report defines a cell surface receptor (OX40) expressed on effector CD4 T cells, which when engaged in conjunction with a danger signal, rescues Ag-stimulated effector cells from activation-induced cell death in vivo. Specifically, three signals were necessary to promote optimal generation of long-lived CD4 T cell memory in vivo: Ag, a danger signal (LPS), and OX40 engagement. Mice treated with Ag or superantigen (SAg) alone produced very few SAg-specific T cells. OX40 ligation or LPS stimulation, enhanced SAg-driven clonal expansion and the survival of responding T cells. However, when SAg was administered with a danger signal at the time of OX40 ligation, a synergistic effect was observed which led to a 60-fold increase in the number of long-lived, Ag-specific CD4 memory T cells. These data lay the foundation for the provision of increased numbers of memory T cells which should enhance the efficacy of vaccine strategies for infectious diseases, or cancer, while also providing a potential target (OX40) to limit the number of auto-Ag-specific memory T cells in autoimmune disease.