Transfer of central nervous system autoantigens and presentation in secondary lymphoid organs

Dendritic cells are thought to regulate tolerance induction vs immunization by transferring Ags and peripheral signals to draining lymph nodes (LN). However, whether myelin Ag transfer and presentation in LN occurs during demyelinating brain disease is unknown. In this study, we demonstrate redistribution of autoantigens from brain lesions to cervical LN in monkey experimental autoimmune encephalomyelitis (EAE) and in multiple sclerosis (MS). Immunohistochemical analysis revealed significantly more cells containing myelin Ags in cervical LN of monkeys with EAE compared with those of healthy control monkeys. Myelin Ags were observed in cells expressing dendritic cell/macrophage-specific markers, MHC class II, and costimulatory molecules. Moreover, these cells were directly juxtaposed to T cells, suggesting that cognate interactions between myelin-containing APC and T cells are taking place in brain-draining LN. Indeed, myelin Ag-reactive T cells were observed in cervical LN from marmosets and rhesus monkeys. Importantly, these findings were paralleled by our findings in human tissue. We observed significantly more myelin Ag-containing cells in LN of individuals with MS compared with those of control individuals. These cells expressed APC markers, as observed in marmosets and rhesus monkeys. These findings suggest that during MS and EAE, modulation of T cell reactivity against brain-derived Ags also takes place in cervical LN and not necessarily inside the brain. A major implication is that novel therapeutic strategies may be targeted to peripheral events, thereby circumventing the blood-brain barrier.     

Correlation of blood T cell and antibody reactivity to myelin proteins with HLA type and lesion localization in multiple sclerosis

Multiple sclerosis (MS) is a chronic inflammatory demyelinating disease of the CNS. The numbers of autoimmune T cells and Abs specific for proteins of CNS myelin are increased in the blood in some patients with MS. The aim of this study was to investigate whether there are correlations between the specificity of the autoimmune responses in the blood, the HLA molecules carried by the patient, and the clinical features of MS, because studies on experimental autoimmune encephalomyelitis, an animal model of MS, indicate that autoimmune responses targeting particular myelin proteins and the genetic background of the animal play a role in determining the pattern of lesion distribution. We tested blood T cell immunoreactivity to myelin proteins in 100 MS patients, 70 healthy controls, and 48 patients with other neurological disorders. Forty MS patients had strongly increased T cell reactivity to one or more myelin Ags. In these 40 patients, the most robust correlation was between CD4(+) T cell reactivity to myelin proteolipid protein residues 184-209 (PLP(184-209)) and development of lesions in the brainstem and cerebellum. Furthermore, carriage of HLA-DR4, -DR7, or -DR13 molecules by MS patients correlated with increased blood T cell immunoreactivity to PLP(184-209), as well as the development of lesions in the brainstem and cerebellum. Levels of PLP(190-209)-specific Abs in the blood also correlated with the presence of cerebellar lesions. These findings show that circulating T cells and Abs reactive against specific myelin Ags can correlate with lesion distribution in MS and suggest that they are of pathogenic relevance.     

Accumulation of MAC387+ macrophages in paracortical areas of lymph nodes in rhesus monkeys acutely infected with simian immunodeficiency virus

We investigated the histological features of lymph nodes, focusing on monocytes/macrophages, in rhesus monkeys (Macaca mulatta) acutely infected with simian immunodeficiency virus (SIV). In monkeys infected with a pathogenic SIV, SIVmac239, MAC387(+) newly blood-derived macrophages markedly increased in number at paracortical areas at 11 to 14 days postinoculation, concomitant with the peak of the primary SIV antigenemia. The MAC387(+) macrophages densely gathered around high endothelial venules and formed cell clusters with CD3(+) T lymphocytes, tingible body macrophages, and plasmacytoid monocytes. In the cell clusters, CD3(+) T lymphocytes which closely adhered to the MAC387(+) macrophages enlarged in size, suggesting a histological manifestation of T-lymphocyte activation by macrophages. By 54 days postinoculation, when SIV antigenemia became undetectable, the MAC387(+) macrophages decreased in number and the cell cluster disappeared from paracortical areas. In contrast, the monkeys infected with a nef-deleted mutant of SIVmac239 showed lower levels of SIV antigenemia and lower numbers of MAC387(+) macrophages in paracortical areas than those infected with SIVmac239. These results indicate that MAC387(+) macrophages accumulate in paracortical areas for the period of the intense primary SIV antigenemia and may play an important role in activating naive T lymphocytes.     

B lymphocytes participate in cross-presentation of antigen following gene gun vaccination

Although endocytosed proteins are commonly presented via the class II MHC pathway to stimulate CD4(+) T cells, professional APCs can also cross-present Ags, whereby these exogenous peptides can be complexed with class I MHC for cross-priming of CD8(+) T cells. Whereas the ability of dendritic cells (DCs) to cross-present Ags is well documented, it is not known whether other APCs may also play a role, or what is the relative contribution of cross-priming to the induction of acquired immunity after DNA immunization. In this study, we compared immune responses generated after gene gun vaccination of mice with DNA vaccine plasmids driven by the conventional CMV promoter, the DC-specific CD11c promoter, or the keratinocyte-specific K14 promoter. The CD11c promoter achieved equivalent expression in CD11c(+) DCs in draining lymph nodes over time, as did a conventional CMV-driven plasmid. However, immunization with DC-restricted DNA vaccines failed to generate protective humoral or cellular immunity to model Ags influenza hemagglutinin and OVA, despite the ability of CD11c(+) cells isolated from lymph nodes to stimulate proliferation of Ag-specific T cells directly ex vivo. In contrast, keratinocyte-restricted vaccines elicited comparable T and B cell activity as conventional CMV promoter-driven vaccines, indicating that cross-priming plays a major role in the generation of immune responses after gene gun immunization. Furthermore, parallel studies in B cell-deficient mu-MT mice demonstrated that B lymphocytes, in addition to DCs, mediate cross-priming of Ag-specific T cells. Collectively, these data indicate that broad expression of the immunogen is required for optimal induction of protective acquired immunity.     

Nasal vaccination with myelin oligodendrocyte glycoprotein reduces stroke size by inducing IL-10-producing CD4+ T cells

Inflammation plays an important role in ischemic stroke and in humans IL-10 may have a beneficial effect in stroke. We mucosally administered myelin oligodendrocyte glycoprotein (MOG) 35-55 peptide to C57BL/6 mice before middle cerebral artery occlusion (MCAO) to induce an anti-inflammatory T cell response directed at CNS myelin. Nasal and oral administration of MOG(35-55) peptide decreased ischemic infarct size at 24 and 72 h after MCAO surgery. Nasal MOG(35-55) peptide was most efficacious and reduced infarct size by 70% at 24 h and by 50% at 72 h (p 相似文献   

Ocular surface APCs are necessary for autoreactive T cell-mediated experimental autoimmune lacrimal keratoconjunctivitis

As specialized sentinels between the innate and adaptive immune response, APCs are essential for activation of Ag-specific lymphocytes, pathogen clearance, and generation of immunological memory. The process is tightly regulated; however, excessive or atypical stimuli may ignite activation of APCs in a way that allows self-Ag presentation to autoreactive T cells in the context of the necessary costimulatory signals, ultimately resulting in autoimmunity. Studies in both animal models and patients suggest that dry eye is a chronic CD4(+) T cell-mediated ocular surface autoimmune-based inflammatory disease. Using a desiccating stress-induced mouse model of dry eye, we establish the fundamental role of APCs for both the generation and maintenance of ocular-specific autoreactive CD4(+) T cells. Subconjunctival administration of liposome-encapsulated clodronate efficiently diminished resident ocular surface APCs, inhibited the generation of autoreactive CD4(+) T cells, and blocked their ability to cause disease. APC-dependent CD4(+) T cell activation required intact draining cervical lymph nodes, as cervical lymphadenectomy also inhibited CD4(+) T cell-mediated dry eye disease. In addition, local depletion of peripheral conjunctival APCs blocked the ability of dry eye-specific CD4(+) T cells to accumulate within the ocular surface tissues, suggesting that fully primed and targeted dry eye-specific CD4(+) T cells require secondary activation by resident ocular surface APCs for maintenance and effector function. These data demonstrate that APCs are necessary for the initiation and development of experimental dry eye and support the standing hypothesis that dry eye is a self-Ag-driven autoimmune disease.     

Quantitative analysis of the acute and long-term CD4(+) T-cell response to a persistent gammaherpesvirus

The murine gammaherpesvirus 68 (MHV-68) replicates in respiratory epithelial cells, where it establishes a persistent, latent infection limited predominantly to B lymphocytes. The virus-specific CD4(+) T-cell response in C57BL/6 mice challenged intranasally with MHV-68 is detected first in the mediastinal lymph nodes and then in the cervical lymph nodes and the spleen. The numbers of MHV-68-specific CD4(+) T cells generated in congenic mice homozygous for disruption of the beta2-microglobulin gene tended to be higher, indicating that the absence of the CD8(+) set in this group resulted in a compensatory response. The peak frequency within the splenic CD4(+) T-cell population may reach 1:50 in the acute response; it then drops to 1:400 to 1:500 within 4 months and stays at that level in the very long term. Sorting for L-selectin (CD62L) expression established that all virus-specific CD4(+) T cells were initially CD62Llow, with >80% maintaining that phenotype for the next 14 months. The overall conclusion is that MHV-68-specific CD4(+) T cells remain activated (CD62Llow) and at a stable frequency in the face of persistent infection.     

Dendritic cells present lytic antigens and maintain function throughout persistent gamma-herpesvirus infection

The activation and maintenance of Ag-specific CD8(+) T cells is central to the long-term control of persistent infections. These killer T cells act to continuously scan and remove reservoirs of pathogen that have eluded the acute immune response. Acutely cleared viral infections depend almost exclusively on dendritic cells (DC) to present Ags to, and to activate, the CD8(+) T cell response. Paradoxically, persistent pathogens often infect professional APCs such as DC, in addition to infecting a broad range of nonprofessional APC, raising the possibility that many cell types could present viral Ags and activate T cells. We addressed whether in persistent viral infection with murine gammaherpesviruses, DC or non-DC, such as B cells and macrophages, were required to maintain the continued activation of Ag-specific CD8(+) T cells. We found that presentation of the surrogate Ag, OVA, expressed under a lytic promoter to CD8(+) T cells during persistent infection was largely restricted to DC, with little contribution from other lymphoid resident cells, such as B cells. This is despite the fact that B cells harbor a very large reservoir of latent virus. Our results support that, during persistent viral infection, continual presentation of lytic Ags by DC leads to T cell activation critical for maintaining CD8(+) T cells capable of limiting persistent viral infection.     

Human leptin enhances activation and proliferation of human circulating T lymphocytes

Leptin is an adipocyte-secreted hormone that centrally regulates weight control. However, leptin receptor is expressed not only in the central nervous system, but also in other systems such as reproductive and hematopoietic tissues. Human leptin has previously been shown to enhance cytokine production by murine peritoneal macrophages and human circulating monocytes. In this paper we have assessed the presence of leptin receptors in peripheral human T lymphocytes and we have studied their functional role. Both CD4(+) and CD8(+) T lymphocytes express leptin receptors. Moreover, we show that human leptin dose-dependently enhances proliferation and activation of human circulating T lymphocytes when they are costimulated by PHA or Con A. Leptin alone was not able to activate T lymphocytes. To confirm a direct effect of leptin on T lymphocytes, monocytes were extracted by adhesion to culture flasks. The early activation surface marker CD69 was then induced in both CD4(+) and CD8(+) T lymphocytes after 8 h stimulation with PHA or Con A. Leptin dose-dependently enhanced stimulated CD69 expression. Moreover, leptin dose-dependently enhanced the expression of the late activation markers CD25 and CD71 in both CD4(+) and CD8(+) T lymphocytes after 48 h stimulation with PHA or Con A. Finally, we have found that leptin modulates CD4(+) T lymphocyte activation toward Th1 phenotype by stimulating the synthesis of IL-2 and IFN-gamma. These results demonstrate the presence of the leptin receptor in human circulating CD4(+) and CD8(+) T lymphocytes and a functional role of leptin as a modulator (enhancer) of lymphocyte stimulation with a shift toward Th1 cytokine-production profile. This function of leptin may have some relevance in the pathophysiology of immunologic alterations related to obesity.     

Identification of a mutated receptor-like protein tyrosine phosphatase kappa as a novel,class II HLA-restricted melanoma antigen

Recent studies increasingly point to a pivotal role of CD4(+) T cells in human anti-tumor immune response. Here we show that lymphocytes purified from a tumor-infiltrated lymph node of a melanoma patient that had remained disease free for 10 years after surgical resection of a lymph node metastasis comprised oligoclonal class II HLA-restricted CD4(+) T cells recognizing the autologous tumor cells in vitro. In fact, the CD4(+) T cell clones isolated from these lymphocytes displayed a tumor-specific, cytotoxic activity in addition to a Th1-like cytokine profile. By a genetic approach, a peptide derived from a mutated receptor-like protein tyrosine phosphatase kappa was identified as a novel HLA-DR10-restricted epitope for all the melanoma-specific CD4(+) T cell clones. The immunogenic peptide was shown to contain the mutated residue that was crucial for T cell recognition and activation. Moreover, a systemic immunity against the mutated peptide was detectable in the patient's peripheral blood T lymphocytes obtained during the disease-free period of follow-up. These findings further support the relevance of CD4(+) T cells directed against mutated epitopes in tumor immunity and provide the rationale for a possible usage of mutated, tumor-specific Ags for immunotherapy of human cancer.     

Initiation of immune responses in brain is promoted by local dendritic cells

The contribution of dendritic cells (DCs) to initiating T cell-mediated immune response in and T cell homing into the CNS has not yet been clarified. In this study we show by confocal microscopy and flow cytometry that cells expressing CD11c, CD205, and MHC class II molecules and containing fluorescently labeled, processed Ag accumulate at the site of intracerebral Ag injection. These cells follow a specific pattern upon migrating out of the brain. To track their pathway out of the CNS, we differentiated DCs from bone marrow of GFP-transgenic mice and injected them directly into brains of naive C57BL/6 mice. We demonstrate that DCs migrate from brain to cervical lymph nodes, a process that can be blocked by fixation or pertussis toxin treatment of the DCs. Injection of OVA-loaded DCs into brain initiates a SIINFEKL (a dominant OVA epitope)-specific T cell response in lymph nodes and spleen, as measured by specific tetramer and LFA-1 activation marker staining. Additionally, a fraction of activated SIINFEKL-specific T cells home to the CNS. Specific T cell homing to the CNS, however, cannot be induced by i.v. injection of OVA-loaded DCs alone. These data suggest that brain-emigrant DCs are sufficient to support activated T cells to home to the tissue of DC origination. Thus, initiation of immune reactivity against CNS Ags involves the migration of APCs from nervous tissue to peripheral lymphoid tissues, similarly to that in other organs.     

Intestinal epithelial antigen induces mucosal CD8 T cell tolerance, activation, and inflammatory response

Intestinal autoimmune diseases are thought to be associated with a breakdown in tolerance, leading to mucosal lymphocyte activation perhaps as a result of encounter with bacterium-derived Ag. To study mucosal CD8(+) T cell activation, tolerance, and polarization of autoimmune reactivity to self-Ag, we developed a novel (Fabpl(4x at -132)-OVA) transgenic mouse model expressing a truncated form of OVA in intestinal epithelia of the terminal ileum and colon. We found that OVA-specific CD8(+) T cells were partially tolerant to intestinal epithelium-derived OVA, because oral infection with Listeria monocytogenes-encoding OVA did not elicit an endogenous OVA-specific MHC class I tetramer(+)CD8(+) T cell response and IFN-gamma-, IL-4-, and IL-5-secreting T cells were decreased in the Peyer's patches, mesenteric lymph nodes, and intestinal mucosa of transgenic mice. Adoptive transfer of OVA-specific CD8(+) (OT-I) T cells resulted in their preferential expansion in the Peyer's patches and mesenteric lymph nodes and subsequently in the epithelia and lamina propria but failed to cause mucosal inflammation. Thus, CFSE-labeled OT-I cells greatly proliferated in these tissues by 5 days posttransfer. Strikingly, OT-I cell-transferred Fabpl(4x at -132)-OVA transgenic mice underwent a transient weight loss and developed a CD8(+) T cell-mediated acute enterocolitis 5 days after oral L. monocytogenes-encoding OVA infection. These findings indicate that intestinal epithelium-derived "self-Ag" gains access to the mucosal immune system, leading to Ag-specific T cell activation and clonal deletion. However, when Ag is presented in the context of bacterial infection, the associated inflammatory signals drive Ag-specific CD8(+) T cells to mediate intestinal immunopathology.     

CD4+CD25+Foxp3+ regulatory T cells are dispensable for controlling CD8+ T cell-mediated lung inflammation

Every person harbors a population of potentially self-reactive lymphocytes controlled by tightly balanced tolerance mechanisms. Failures in this balance evoke immune activation and autoimmunity. In this study, we investigated the contribution of self-reactive CD8(+) T lymphocytes to chronic pulmonary inflammation and a possible role for naturally occurring CD4(+)CD25(+)Foxp3(+) regulatory T cells (nTregs) in counterbalancing this process. Using a transgenic murine model for autoimmune-mediated lung disease, we demonstrated that despite pulmonary inflammation, lung-specific CD8(+) T cells can reside quiescently in close proximity to self-antigen. Whereas self-reactive CD8(+) T cells in the inflamed lung and lung-draining lymph nodes downregulated the expression of effector molecules, those located in the spleen appeared to be partly Ag-experienced and displayed a memory-like phenotype. Because ex vivo-reisolated self-reactive CD8(+) T cells were very well capable of responding to the Ag in vitro, we investigated a possible contribution of nTregs to the immune control over autoaggressive CD8(+) T cells in the lung. Notably, CD8(+) T cell tolerance established in the lung depends only partially on the function of nTregs, because self-reactive CD8(+) T cells underwent only biased activation and did not acquire effector function after nTreg depletion. However, although transient ablation of nTregs did not expand the population of self-reactive CD8(+) T cells or exacerbate the disease, it provoked rapid accumulation of activated CD103(+)CD62L(lo) Tregs in bronchial lymph nodes, a finding suggesting an adaptive phenotypic switch in the nTreg population that acts in concert with other yet-undefined mechanisms to prevent the detrimental activation of self-reactive CD8(+) T cells.     

In vivo differentiated cytokine-producing CD4(+) T cells express functional CCR7

Chemokines and their receptors fulfill specialized roles in inflammation and under homeostatic conditions. CCR7 and its ligands, CCL19 and CCL21, are involved in lymphocyte recirculation through secondary lymphoid organs and additionally navigate lymphocytes into distinct tissue compartments. The role of CCR7 in the migration of polarized T effector/memory cell subsets in vivo is still poorly understood. We therefore analyzed murine and human CD4(+) cytokine-producing cells developed in vivo for their chemotactic reactivity to CCR7 ligands. The responses of cells producing cytokines, such as IFN-gamma, IL-4, and IL-10, as well as of subsets defined by memory or activation markers were comparable to that of naive CD4(+) cells, with slightly lower reactivity in cells expressing IL-10 or CD69. This indicates that CCR7 ligands are able to attract naive as well as the vast majority of activated and effector/memory T cell stages. Chemotactic reactivity of these cells toward CCL21 was absent in CCR7-deficient cells, proving that effector cells do not use alternative receptors for this chemokine. Th1 cells generated from CCR7(-/-) mice failed to enter lymph nodes and Peyer's patches, but did enter a site of inflammation. These findings indicate that CD4(+) cells producing effector cytokines upon stimulation retain the capacity to recirculate through lymphoid tissues via CCR7.     

CD8+ T cells mediate recovery and immunopathology in West Nile virus encephalitis

C57BL/6J mice infected intravenously with the Sarafend strain of West Nile virus (WNV) develop a characteristic central nervous system (CNS) disease, including an acute inflammatory reaction. Dose response studies indicate two distinct kinetics of mortality. At high doses of infection (10(8) PFU), direct infection of the brain occurred within 24 h, resulting in 100% mortality with a 6-day mean survival time (MST), and there was minimal destruction of neural tissue. A low dose (10(3) PFU) of infection resulted in 27% mortality (MST, 11 days), and virus could be detected in the CNS 7 days postinfection (p.i.). Virus was present in the hypogastric lymph nodes and spleens at days 4 to 7 p.i. Histology of the brains revealed neuronal degeneration and inflammation within leptomeninges and brain parenchyma. Inflammatory cell infiltration was detectable in brains from day 4 p.i. onward in the high-dose group and from day 7 p.i. in the low-dose group, with the severity of infiltration increasing over time. The cellular infiltrates in brain consisted predominantly of CD8(+), but not CD4(+), T cells. CD8(+) T cells in the brain and the spleen expressed the activation markers CD69 early and expressed CD25 at later time points. CD8(+) T-cell-deficient mice infected with 10(3) PFU of WNV showed increased mortalities but prolonged MST and early infection of the CNS compared to wild-type mice. Using high doses of virus in CD8-deficient mice leads to increased survival. These results provide evidence that CD8(+) T cells are involved in both recovery and immunopathology in WNV infection.     

Presentation of alpha B-crystallin to T cells in active multiple sclerosis lesions: an early event following inflammatory demyelination

In the development of multiple sclerosis (MS), (re)activation of infiltrating T cells by myelin-derived Ags is considered to be a crucial step. Previously, alpha B-crystallin has been shown to be an important myelin Ag to human T cells. Since alpha B-crystallin is an intracellular heat shock protein, the question arises at what stage, if any, during lesional development in MS this Ag becomes available for CD4+ T cells. In 3 of 10 active MS lesions, alpha B-crystallin could be detected inside phagocytic vesicles of perivascular macrophages, colocalizing with myelin basic protein and myelin oligodendrocyte glycoprotein (MOG). Although the detectability of MOG in phagosomes is considered as a marker for very recent demyelination, MOG was detected in more macrophages and in more lesions than alpha B-crystallin. The disappearance of alpha B-crystallin from macrophages even before MOG was confirmed by in vitro studies; within 6 h after myelin-uptake alpha B-crystallin disappears from the phagosomes. Alpha B-crystallin-containing macrophages colocalized with infiltrating T cells and they were characterized by expression of MHC class II, CD40, and CD80. To examine functional presentation of myelin Ags to T cells, purified macrophages were pulsed in vitro with whole myelin membranes. These macrophages activated both myelin-primed and alpha B-crystallin-primed T cells in terms of proliferation and IFN-gamma secretion. In addition, alpha B-crystallin-pulsed macrophages activated myelin-primed T cells to the same extent as myelin-pulsed macrophages, whereas myelin basic protein-pulsed macrophages triggered no response at all. These data indicate that, in active MS lesions, alpha B-crystallin is available for functional presentation to T cells early during inflammatory demyelination.     

Local intrahepatic CD8+ T cell activation by a non-self-antigen results in full functional differentiation

The response of T cells to liver Ags sometimes results in immune tolerance. This has been proposed to result from local, intrahepatic priming, while the expression of the same Ag in liver-draining lymph nodes is believed to result in effective immunity. We tested this model, using an exogenous model Ag expressed only in hepatocytes, due to infection with an adeno-associated virus vector. T cell activation was exclusively intrahepatic, yet in contrast to the predictions of the current model, this resulted in clonal expansion, IFN-gamma synthesis, and cytotoxic effector function. Local activation of naive CD8(+) T cells can therefore cause full CD8(+) T cell activation, and hepatocellular presentation cannot be used to explain the failure of CTL effector function against some liver pathogens such as hepatitis C.     

Quetiapine, an Atypical Antipsychotic, Is Protective against Autoimmune-Mediated Demyelination by Inhibiting Effector T Cell Proliferation

Quetiapine (Que), a commonly used atypical antipsychotic drug (APD), can prevent myelin from breakdown without immune attack. Multiple sclerosisis (MS), an autoimmune reactive inflammation demyelinating disease, is triggered by activated myelin-specific T lymphocytes (T cells). In this study, we investigated the potential efficacy of Que as an immune-modulating therapeutic agent for experimental autoimmune encephalomyelitis (EAE), a mouse model for MS. Que treatment was initiated on the onset of MOG(35-55) peptide induced EAE mice and the efficacy of Que on modulating the immune response was determined by Flow Cytometry through analyzing CD4(+)/CD8(+) populations and the proliferation of effector T cells (CD4(+)CD25(-)) in peripheral immune organs. Our results show that Que dramatically attenuates the severity of EAE symptoms. Que treatment decreases the extent of CD4(+)/CD8(+) T cell infiltration into the spinal cord and suppresses local glial activation, thereby diminishing the loss of mature oligodendrocytes and myelin breakdown in the spinal cord of EAE mice. Our results further demonstrate that Que treatment decreases the CD4(+)/CD8(+) T cell populations in lymph nodes and spleens of EAE mice and inhibits either MOG(35-55) or anti-CD3 induced proliferation as well as IL-2 production of effector T cells (CD4(+)CD25(-)) isolated from EAE mice spleen. Together, these findings suggest that Que displays an immune-modulating role during the course of EAE, and thus may be a promising candidate for treatment of MS.     

Resistance to apoptosis in HIV-infected CD4+ T lymphocytes is mediated by macrophages: role for Nef and immune activation in viral persistence

Apoptosis or programmed cell death may play a critical role in AIDS pathogenesis through depletion of both CD4(+) and CD8(+) T lymphocytes. Using a reporter virus, a recombinant HIV infectious clone expressing the green fluorescent protein (GFP), apoptosis was measured in productively infected CD4(+) T lymphocytes, in the presence and absence of autologous macrophages. The presence of macrophages in the culture increased the frequency of nonapoptotic GFP-positive productively infected CD4(+) T lymphocytes. The appearance of nonapoptotic productively infected CD4(+) T lymphocytes in the culture required intercellular contacts between macrophages and PBLs and the expression of the HIV Nef protein. The presence of macrophages did not reduce apoptosis when CD4(+) T lymphocytes were infected with a GFP-tagged virus deleted for the nef gene. TNF-alpha (TNF) expressed on the surface of macrophages prevented apoptosis in nef-expressing, productively infected CD4(+) T lymphocytes. Similarly, following TNF stimulation, apoptosis was diminished in Jurkat T cells transfected with a nef-expressing plasmid. TNF stimulation of nef-expressing Jurkat T cells resulted in NF-kappaB hyperactivation, which has been shown to deliver anti-apoptotic signals. Our results indicate that intercellular contacts with macrophages increase the rate of productively infected nonapoptotic CD4(+) T lymphocytes. The survival of productively infected CD4(+) T lymphocytes requires Nef expression as well as activation by TNF expressed on the surface of macrophages and might participate in the formation and maintenance of viral reservoirs in HIV-infected persons.     

APCs in the liver and spleen recruit activated allogeneic CD8+ T cells to elicit hepatic graft-versus-host disease

Host APCs are required for initiating T cell-dependent acute graft-vs-host disease (GVHD), but the role of APCs in the effector phase of acute GVHD is not known. To measure the effect of tissue-resident APCs on the local development of acute GVHD, we selectively depleted host macrophages and DCs from the livers and spleens, but not from the skin, peripheral lymph nodes (PLN), or mesenteric lymph nodes (MLN), of C57BL/6 (B6) mice by i.v. administration of liposomal clodronate before allogeneic bone marrow transplantation. Depletion of host hepatic and splenic macrophages and DCs significantly inhibited the proliferation of donor C3H.SW CD8(+) T cells in the spleen, but not in the PLN or MLN, of B6 mice. Such organ-selective depletion of host tissue APCs also markedly reduced the trafficking of allogeneic CD8(+) T cells into the livers and spleens, but not PLN and MLN, of B6 recipients compared with that of the control mice. Acute hepatic, but not cutaneous, GVHD was inhibited as well, resulting in improved survival of liposomal clodronate-treated B6 recipients. When C3H.SW CD8(+) T cells were activated in normal B6 recipients, recovered, and adoptively transferred into secondary B6 recipients, activated donor CD8(+) T cells rapidly migrated into the livers and spleens of control B6 recipients but were markedly decreased in B6 mice that were depleted of hepatic and splenic macrophages and DCs. Thus, tissue-resident APCs control the local recruitment of allo-reactive donor T cells and the subsequent development of acute GVHD.