Autoimmunity in the central nervous system: mechanisms of antigen presentation and recognition

Pediatric postviral autoimmune disorders of the CNS

Infections caused by various viruses, mainly belonging to the Herpesviridae family, can trigger the autoimmune process in the CNS in children. This can break brain immune tolerance and induce many molecular and cellular pathways of the immune response. This can lead to the appearance of neuronal auto-antibodies to intracellular, cell-surface or extracellular synaptic antigens. Children may also display a wide spectrum of neurological problems from encephalitis to obsessive–compulsive or tic disorders. In these cases, patients rarely respond to traditional treatment, based on antiviral or/and symptomatic drugs, but early immunotherapy is very effective. The implementation of routine immune tests in all children with acute neurological disorders should be recommended.

Autoimmune diseases: Role of steroid hormones

Autoimmune diseases (AIDs) are a heterogeneous group of disorders in terms of clinical manifestations, pathogenesis, and prevalence, and there is no agreement to date on a common classification. Adaptive immune responses are responsible for the existence of AIDs, although innate immunity is also involved in misguiding the immune response against self-antigens. Hormones, in general, and in particular steroid hormones, play a critical role in the physiology and pathology of the immune system, especially in adaptive immunity. Hormonal factors, alone or in relation to age, sex, and reproductive status, are involved in conditioning the onset of a number of AIDs. There is a well-defined sexual dimorphism for human AIDs. At the same time, the classic view has been that steroid hormones have well-defined effects, with one type, estrogens, being "pro-inflammatory" and the other two progestogens (progesterone and its synthetic analogs) and androgens being "anti-inflammatory." Although this view has been considered too simplistic and seems contradicted by numerous observations, it remains valid: progestogens and androgens are immunosuppressive and therefore protective against AIDs, whereas estrogens are immune-stimulatory and therefore pathogenic in AIDs.

Differential regulation of NSC phenotype and genotype by chronically activated microglia within cocultures

Under disease or injury conditions in the central nervous system (CNS), activated microglia release cytokines and chemokines to modulate the microenvironment and influence tissue remodeling. To exploit the full potential of neural stem cell (NSC) transplantation approaches, a permissive microenvironment needs to be created for their survival, homing and differentiation. To investigate the role of chronically activated microglia in the fate of NSCs, spontaneously immortalized murine microglial cells (SIM-A9) were cocultured with embryonic murine cortical NSCs on 2D substrates or within 3D gels. Standalone NSC cultures served as controls. Cytokines and chemokines released by NSCs and SIM-A9 cells in standalone and cocultures were quantified. Coculturing with SIM-A9 cells suppressed NSC viability, neurite outgrowth, neural differentiation and TUJ1 gene expression, and promoted glia formation in both 2D and 3D cultures, over a 10-day period. The seven most-abundantly released analytes by microglia (MCP-1, MIP2, G-CSF, MIP-1α, MIP-1β, TNF-α, IL-6) were tested for their individual effects on NSCs, to investigate if the outcomes in cocultures were due to the synergistic effects of analytes or the influence of any individual analyte. All the seven analytes significantly suppressed cell survival compared to controls, but exposure to MIP-1β, IL-6, or MCP-1 enhanced neurite outgrowth and neural lineage commitment. Results attest to (i) the strong role of activated microglia in regulating NSC fate, (ii) the utility of selective analytes released by activated microglia in promoting neurogenesis and neuritogenesis, and (iii) the need to protect transplanted NSCs from the host inflammatory microenvironment to ensure their survival and functionality in treating neurological disorders.

Assessment of neuronal autoantibodies in patients with small cell lung cancer treated with chemotherapy with or without ipilimumab

Small-cell lung cancer (SCLC) is often associated with paraneoplastic syndromes. To assess the role of anti-neuronal autoantibodies (NAAs) as biomarkers of treatment outcome, we assessed NAAs in serial samples from SCLC patients treated with chemoimmunotherapy compared to chemotherapy alone. We evaluated 2 cohorts: in cohort 1 (C1), 47 patients received standard platinum/etoposide, and in cohort 2 (C2), 38 patients received ipilimumab, carboplatin and etoposide. Serum samples at baseline and subsequent time points were analyzed for the presence of NAAs. NAAs were detected at baseline in 25 patients (53.2%) in C1 and in 20 patients (52.6%) in C2 (most frequently anti-Sox1). NAA at baseline was associated with limited disease (75% vs 50%; p: 0.096) and better overall survival (15.1 m vs 11.7 m; p: 0.032) in C1. Thirteen patients (28.9%) showed 2 or more reactivities before treatment; this was associated with worse PFS (5.5 m vs 7.3 m; p: 0.005) in patients treated with chemoimmunotherapy. NAA titers decreased after therapy in 68.9% patients, with no differential patterns of change between cohorts. Patients whose NAA titer decreased after treatment, showed longer OS [18.5 m (95% CI: 15.8 - 21.2)] compared with those whose NAA increased [12.3 m (95% CI: 8.1 - 16.5; p 0.049)], suggesting that antibody levels correlate to tumor load. Our findings reinforce the role of NAAs as prognostic markers and tumor activity/burden in SCLC, warrant further investigation in their predictive role for immunotherapy and raise concern over the use of immunotherapy in patients with more than one anti-NAA reactivity.

Adoptive transfer of M2 macrophages promotes locomotor recovery in adult rats after spinal cord injury

Classically activated pro-inflammatory (M1) and alternatively activated anti-inflammatory (M2) macrophages populate the local microenvironment after spinal cord injury (SCI). The former type is neurotoxic while the latter has positive effects on neuroregeneration and is less toxic. In addition, while the M1 macrophage response is rapidly induced and sustained, M2 induction is transient. A promising strategy for the repair of SCI is to increase the fraction of M2 cells and prolong their residence time. This study investigated the effect of M2 macrophages induced from bone marrow-derived macrophages on the local microenvironment and their possible role in neuroprotection after SCI. M2 macrophages produced anti-inflammatory cytokines such as interleukin (IL)-10 and transforming growth factor β and infiltrated into the injured spinal cord, stimulated M2 and helper T (Th)2 cells, and produced high levels of IL-10 and -13 at the site of injury. M2 cell transfer decreased spinal cord lesion volume and resulted in increased myelination of axons and preservation of neurons. This was accompanied by significant locomotor improvement as revealed by Basso, Beattie and Bresnahan locomotor rating scale, grid walk and footprint analyses. These results indicate that M2 adoptive transfer has beneficial effects for the injured spinal cord, in which the increased number of M2 macrophages causes a shift in the immunological response from Th1- to Th2-dominated through the production of anti-inflammatory cytokines, which in turn induces the polarization of local microglia and/or macrophages to the M2 subtype, and creates a local microenvironment that is conducive to the rescue of residual myelin and neurons and preservation of neuronal function.

The kinetics of myelin antigen uptake by myeloid cells in the central nervous system during experimental autoimmune encephalomyelitis

Induction of experimental autoimmune encephalomyelitis (EAE) in susceptible animals requires reactivation of encephalitogenic CD4(+) T cells by APCs in the CNS. However, it has remained unresolved from where APCs in the CNS acquire myelin Ag for T cell activation and under which conditions, that is, whether only during EAE or also in the naive CNS. In this study, we investigated the kinetics of myelin Ag uptake by CNS APCs during EAE and in the naive CNS. Our results show that during EAE CX3CR1(+)CD11b(+) microglia were the first APCs in the CNS to contain myelin Ag upon induction of disease, albeit in very small numbers. Dendritic cells (DCs) arrived in the CNS in sizable numbers significantly later (day 5 postimmunization), without detectable myelin Ag, but acquired it by day 7 postimmunization. Furthermore, a sharp increase in neuroantigen-containing DCs coincided with the onset of EAE symptoms. Importantly, in naive mice a low but consistent number of microglia contained myelin Ag, suggesting release by oligodendrocytes under steady state conditions. Although microglia isolated from naive brain and spinal cord did not elicit a strong CD4(+) T cell response in vitro, myelin Ag-containing microglia may still play a local role in modulating encephalitogenic CD4(+) T cell responses in early EAE prior to the arrival of other professional APCs, such as DCs. Finally, newly arriving DCs in the CNS not yet loaded with myelin Ag before the onset of EAE may be a potential therapeutic target.

Analysis of the host transcriptome from demyelinating spinal cord of murine coronavirus-infected mice

Persistent infection of the mouse central nervous system (CNS) with mouse hepatitis virus (MHV) induces a demyelinating disease pathologically similar to multiple sclerosis and is therefore used as a model system. There is little information regarding the host factors that correlate with and contribute to MHV-induced demyelination. Here, we detail the genes and pathways associated with MHV-induced demyelinating disease in the spinal cord. High-throughput sequencing of the host transcriptome revealed that demyelination is accompanied by numerous transcriptional changes indicative of immune infiltration as well as changes in the cytokine milieu and lipid metabolism. We found evidence that a Th1-biased cytokine/chemokine response and eicosanoid-derived inflammation accompany persistent MHV infection and that antigen presentation is ongoing. Interestingly, increased expression of genes involved in lipid transport, processing, and catabolism, including some with known roles in neurodegenerative diseases, coincided with demyelination. Lastly, expression of several genes involved in osteoclast or bone-resident macrophage function, most notably TREM2 and DAP12, was upregulated in persistently infected mouse spinal cord. This study highlights the complexity of the host antiviral response, which accompany MHV-induced demyelination, and further supports previous findings that MHV-induced demyelination is immune-mediated. Interestingly, these data suggest a parallel between bone reabsorption by osteoclasts and myelin debris clearance by microglia in the bone and the CNS, respectively. To our knowledge, this is the first report of using an RNA-seq approach to study the host CNS response to persistent viral infection.

Peripheral immune contributions to the maintenance of central glial activation underlying neuropathic pain

Recent evidence implicates an adaptive immune response in the central nervous system (CNS) mechanisms of neuropathic pain. This review identifies how neuropathic pain alters CNS immune privilege to facilitate T cell infiltration. Once in the CNS, T cells may interact with the local antigen presenting cells, microglia, via the major histocompatibility complex and the costimulatory molecules CD40 and B7. In this way, T cells may contribute to the maintenance of neuropathic pain through pro-inflammatory interactions with microglia and by facilitating the activation of astrocytes in the spinal dorsal horn. Based on the evidence presented in this review, we suggest that this bidirectional, pro-inflammatory system of neurons, glia and T cells in neuropathic pain should be renamed the pentapartite synapse, and identifies the latest member as a potential disease-modifying therapeutic target.

Small-cell lung cancer-associated autoantibodies: potential applications to cancer diagnosis, early detection, and therapy

Small-cell lung cancer (SCLC) is the most aggressive lung cancer subtype and lacks effective early detection methods and therapies. A number of rare paraneoplastic neurologic autoimmune diseases are strongly associated with SCLC. Most patients with such paraneoplastic syndromes harbor high titers of antibodies against neuronal proteins that are abnormally expressed in SCLC tumors. These autoantibodies may cross-react with the nervous system, possibly contributing to autoimmune disease development. Importantly, similar antibodies are present in many SCLC patients without autoimmune disease, albeit at lower titers. The timing of autoantibody development relative to cancer and the nature of the immune trigger remain to be elucidated. Here we review what is currently known about SCLC-associated autoantibodies, and describe a recently developed mouse model system of SCLC that appears to lend itself well to the study of the SCLC-associated immune response. We also discuss potential clinical applications for these autoantibodies, such as SCLC diagnosis, early detection, and therapy.

MHC class II exacerbates demyelination in vivo independently of T cells

We have shown previously the importance of MHC class II for central nervous system remyelination; however, the function of MHC class II during cuprizone-induced demyelination has not been examined. Here, we show that I-A(beta)-/- mice exhibit significantly reduced inflammation and demyelination. RAG-1(1/1) mice are indistinguishable from controls, indicating T cells may not play a role. The role of MHC class II depends on an intact cytoplasmic tail that leads to the production of IL-1beta, TNF-alpha, and nitric oxide, and oligodendrocyte apoptosis. Thus, the function of MHC class II cytoplasmic tail appears to increase microglial proliferation and activation that exacerbates demyelination.

Effects of autoimmunity on recovery of function in adult rats following spinal cord injury

The central nervous system (CNS) is considered to be an immune-privileged site. For a long time, autoimmunity-induced inflammation has been viewed as an important mediator of secondary damage in the CNS following injury. However, other studies also suggest that autoimmunity is protective and beneficial. To investigate whether protective autoimmunity is present following spinal cord injury (SCI), we employed neonatally thymectomized (Tx) rats which contain few T lymphocytes in their peripheral blood, and passively immunized them with T lymphocytes activated by myelin basic protein (MBP) or spinal cord homogenate (SCH). Here we report that, among Tx, sham-Tx (sTx) and normal rats that received a contusive SCI, no significant histological and behavioral differences were found, suggesting that the endogenous T lymphocytes had no significant influence on the pathogenesis of secondary SCI. In rats passively immunized with MBP- or SCH-activated T cells (MBP-T or SCH-T, respectively), similar numbers of CD4(+) T cells were found to infiltrate into the injured spinal cords. However, only the MBP-T immunization showed neuroprotection, evidenced by the reduction of post-traumatic neuronal losses and improvement of functional recovery. These results collectively suggest that not all T lymphocytes against CNS antigens are neuroprotective and that a subpopulation of them, such as those of MBP-T cells, could be beneficial for SCI repair.

Autoantibodies to alpha-synuclein in inherited Parkinson's disease

Neurodegeneration in Parkinson's disease (PD) is accompanied by a local immune reaction in the affected brain regions. It is well established that alpha-synuclein is directly implicated in the pathogenesis of PD. Development of the disease is often associated with changes of expression and cellular compartmentalisation of this protein; moreover, its oligomers or protofibrils are often released to the CSF and plasma of patients. Aggregated alpha-synuclein can trigger the activation of microglia; however, its capacity to induce production of specific autoantibodies (AAb) has not been assessed. In this study, we examined the presence of AAb against synuclein family members in the peripheral blood serum of PD patients and control individuals. Presence of AAb against beta-synuclein or gamma-synuclein showed no association with PD. Multi-epitopic AAb against alpha-synuclein were detected in 65% of all patients tested and their presence strongly correlated with an inherited mode of the disease but not with other disease-related factors. The frequency of the presence of AAb in the studied group of patients with sporadic form of PD was not significantly different from the frequency in the control group but very high proportion (90%) of patients with familial form of the disease were positive for AAb against alpha-synuclein. We hypothesise that these AAb could be involved in pathogenesis of the inherited form of PD.

Remnant epitopes, autoimmunity and glycosylation

The role of extracellular proteolysis in innate and adaptive immunity and the interplay between cytokines, chemokines and proteinases are gradually becoming recognized as critical factors in autoimmune processes. Many of the involved proteinases, including those of the plasminogen activator and matrix metalloproteinase cascades, and also several cytokines and chemokines, are glycoproteins. The stability, interactions with inhibitors or receptors, and activities of these molecules are fine-controlled by glycosylation. We studied gelatinase B or matrix metalloproteinase-9 (MMP-9) as a glycosylated enzyme involved in autoimmunity. In the joints of rheumatoid arthritis patients, CXC chemokines, such as interleukin-8/CXCL8, recruit and activate neutrophils to secrete prestored neutrophil collagenase/MMP-8 and gelatinase B/MMP-9. Gelatinase B potentiates interleukin-8 at least tenfold and thus enhances neutrophil and lymphocyte influxes to the joints. When cartilage collagen type II is cleaved at a unique site by one of several collagenases (MMP-1, MMP-8 or MMP-13), it becomes a substrate of gelatinase B. Human gelatinase B cleaves the resulting two large collagen fragments into at least 33 peptides of which two have been shown to be immunodominant, i.e., to elicit activation and proliferation of autoimmune T cells. One of these two remnant epitopes contains a glycan which is important for its immunoreactivity. In addition to the role of gelatinase B as a regulator in adaptive immune processes, we have also demonstrated that it destroys interferon-beta, a typical innate immunity effector molecule and therapeutic cytokine in multiple sclerosis. Furthermore, glycosylated interferon-beta, expressed in Chinese hamster ovary cells, was more resistant to this proteolysis than recombinant interferon-beta from bacteria. These data not only prove that glycosylation of proteins is mechanistically important in the pathogenesis of autoimmune diseases, but also show that targeting of glycosylated proteinases or the use of glycosylated cytokines seems also critical for the treatment of autoimmune diseases.

The relationship between immunodominance, DM editing, and the kinetic stability of MHC class II:peptide complexes

Immunodominance refers to the restricted antigen specificity of T cells detected in the immune response after immunization with complex antigens. Despite the presence of many potential peptide epitopes within these immunogens, the elicited T-cell response apparently focuses on a very limited number of peptides. Over the last two decades, a number of distinct explanations have been put forth to explain this very restricted specificity of T cells, many of which suggest that endosomal antigen processing restricts the array of peptides available to recruit CD4 T cells. In this review, we present evidence from our laboratory that suggest that immunodominance in CD4 T-cell responses is primarily due to an intrinsic property of the peptide:class II complexes. The intrinsic kinetic stability of peptide:class II complexes controls DM editing within the antigen-presenting cells and thus the initial epitope density on priming dendritic cells. Additionally, we hypothesize that peptides that possess high kinetic stability interactions with class II molecules display persistence at the cell surface over time and will more efficiently promote T-cell signaling and differentiation than competing, lower-stability peptides contained within the antigen. We discuss this model in the context of the existing data in the field of immunodominance.

Brain activation of monocyte lineage cells: brain-derived soluble factors differentially regulate BV2 microglia and peripheral macrophage immune functions

Brain injury and subsequent neurodegeneration are often associated with infiltrating leukocytes and the activation of microglia as well as other infiltrating cells. However, the characteristics of activation are poorly understood. The objective of this study was to further the understanding of brain regulation of microglial activation. We used an organotypic coculture paradigm to assess how brain-derived soluble factors modulate microglia and peripheral macrophage activation through microscopy and flow cytometry techniques. In the presence of brain-derived soluble factors, the BV2 microglia cell line increased MHC II and phagocytic receptor (Fcgamma II/III) expression. The increased expression correlated with a functional increase in phagocytic activity, but did not correlate with an increase in allostimulation ability. Furthermore, this interaction was selective to an interaction between brain-derived soluble factor(s) and BV2 microglia, since it was not observed in the ANA1 macrophage cell line or in primary peritoneal macrophages. The results indicated that brain-derived soluble factor(s) modulate microglial activation in a manner that is distinct from the effects on peripheral macrophages. Moreover, our results suggest that inflammatory events associated with some types of brain injury may be induced by the brain without dependence on infiltrating peripheral macrophages or T lymphocytes.

T-cell immune responses in the brain and their relevance for cerebral malignancies

In order that cellular immune responses afford protection without risk to sensitive normal tissue, they must be adapted to individual tissues of the body. Nowhere is this more critical than for the brain, where various passive and active mechanisms maintain a state of immune privilege that can limit high magnitude immune responses. Nevertheless, it is now clear that immune responses are induced to antigens in the brain, including those expressed by cerebral malignancies. We discuss hypotheses of how this can occur, although details such as which antigen presenting cells are involved remain to be clarified. Antitumor responses induced spontaneously are insufficient to eradicate malignant astrocytomas; many studies suggest that this can be explained by a combination of low level immune response induction and tumor mediated immunosuppression. A clinical objective currently pursued is to use immunotherapy to ameliorate antitumour immunity. This will necessitate a high level immune response to ensure sufficient effector cells reach the tumor bed, focused cytotoxicity to eradicate malignant cells with little collateral damage to critical normal cells, and minimal inflammation. To achieve these aims, priority should be given to identifying more target antigens in astrocytoma and defining those cells present in the brain parenchyma that are essential to maintain antitumour effector function without exacerbating inflammation. If we are armed with better understanding of immune interactions with brain tumor cells, we can realistically envisage that immunotherapy will one day offer hope to patients with currently untreatable neoplastic diseases of the CNS.

The immunological properties of adult hippocampal progenitor cells

Adult hippocampal progenitor cells (AHPCs) derived from mature rats were studied in mixed co-cultures and shown not to elicit a proliferative response from human peripheral blood mononuclear cells (PBMCs) or allogeneic spleen cells. FACS analysis revealed low class I and no detectable class II (Ia) MHC expression by these cells. RT-PCR showed that AHPCs express the anti-inflammatory cytokine TGF-beta1. AHPCs did not, however, significantly impede the proliferation of OKT3- or PHA-stimulated PBMCs. Taken together, these results indicate that AHPCs are non-immunogenic in vitro. This is consistent with their pattern of MHC expression and does not require an active immunosuppressive mechanism.

Protective effect of systemic treatment with cyclosporine A after global ischemia in rats

Systemic administration of cyclosporine A (CsA) in single daily doses provides a powerful protection to the ischemic rat brain only to sites where the blood-brain barrier (BBB) is disrupted. This study was aimed at evaluating the effectiveness of prolonged treatment and multiple daily doses of systemic CsA following transient global ischemia in rats without BBB breakdown. Multiple daily doses selectively enhanced cell survival at 7-day recovery in regions displaying delayed neuronal death (DND). The effect was dose dependent, enhanced by prolonging the treatment or further fractionating daily doses, and not accompanied by drug-induced hypothermia. These results suggest that CsA-susceptible immune mediators of DND may be active during the first days following transient global ischemia. Conversely, postischemic hyperthermia may enhance and/or perpetuate similar mechanisms and trigger Alzheimer-like neurodegeneration, as recently reported.

Expression of Golli mRNA during development in primary immune lymphoid organs of the rat

The gene-of-the-oligodendrocyte lineage (Golli)-MBP transcription unit contains three Golli-specific exons together with eight exons of the "classical" myelin basic protein (MBP) gene, yielding alternatively spliced proteins which share amino acid sequence with MBP. Unlike MBP, a late antigen expressed only in the nervous system, Golli gene products are expressed pre- and post-natally at many sites. In this study, we determined the sequence of Golli in rat by RT-PCR and 5' RACE and showed that Golli sequences are expressed in primary lymphoid organs as early as e16.5, which could explain the anergic rat T cell response we previously observed in Golli-induced meningitis.

Beneficial autoimmune T cells and posttraumatic neuroprotection

Injuries of the central nervous system (CNS) lead to an inevitable and irreversible loss of function because of the lack of neurogenesis, poor regeneration, and the spread of degeneration. In most tissues, protection and repair are the function of the immune system. It has long been thought that this does not apply to the CNS, where--because of its immune-privileged character--any immune activity was assumed to be detrimental. We have recently proposed, however, that provided care is taken to avoid the attendant risks, both repair and protection of injured CNS neurons can benefit from immune intervention. In the following I will summarize the data that led to this concept and describe the evidence supporting it.

Vaccination for neuroprotection in the mouse optic nerve: implications for optic neuropathies

T-cell autoimmunity to myelin basic protein was recently shown to be neuroprotective in injured rat optic nerves. In the present study, using the mouse optic nerve, we examined whether active immunization rather than passive transfer of T-cells can be beneficial in protecting retinal ganglion cells (RGCs) from post-traumatic death. Before severe crush injury of the optic nerve, SJL/J and C3H.SW mice were actively immunized with encephalitogenic or nonencephalitogenic peptides of proteolipid protein (PLP) or myelin oligodendrocyte glycoprotein (MOG), respectively. At different times after the injury, the numbers of surviving RGCs in both strains immunized with the nonencephalitogenic peptides pPLP 190-209 or pMOG 1-22 were significantly higher than in injured controls treated with the non-self-antigen ovalbumin or with a peptide derived from beta-amyloid, a non-myelin-associated protein. Immunization with the encephalitogenic myelin peptide pPLP 139-151 was beneficial only when the disease it induced, experimental autoimmune encephalomyelitis, was mild. The results of this study show that survival of RGCs after axonal injury can be enhanced by vaccination with an appropriate self-antigen. Furthermore, the use of nonencephalitogenic myelin peptides for immunization apparently allows neuroprotection without incurring the risk of an autoimmune disease. Application of these findings might lead to a promising new approach for treating optic neuropathies such as glaucoma.

Intracranial paracrine interleukin-2 therapy stimulates prolonged antitumor immunity that extends outside the central nervous system

To explore the potential efficacy of local cytokine delivery against tumors in the central nervous system (CNS), C57BL6 mice were simultaneously given intracranial injections of tumor challenge and of irradiated B16F10 melanoma cells transduced to secrete interleukin-2 (IL-2). Intracranial IL-2 therapy generated antitumor responses capable of extending the survival of animals that received simultaneous intracranial tumor challenge either locally or at distant sites in the brain. Nontransduced melanoma cells had little effect. Animals that survived intracranial IL-2 therapy and tumor challenge showed prolonged survival compared with controls when challenged with a second tumor dose 70 days after initial treatment. In addition, animals that rejected intracranial tumors were also protected from tumor growth upon rechallenge at sites outside the CNS (i.e., subcutaneous tumor challenge). Conversely, identical or 10-fold larger doses of IL-2-transduced cells administered by subcutaneous injection failed to generate protection against intracranial tumor challenges. Elimination of T-cell and natural killer (NK) subsets using gene knockout mice and antibody-depletion techniques demonstrated that NK cells were most important for the initial antitumor response, whereas CD4+ T-cells were not necessary. These studies demonstrate that local IL-2 therapy in the brain not only generates an immediate local antitumor immune response, but also establishes long-term immunologic memory capable of eliminating subsequent tumor challenges within and outside of the CNS. Furthermore, the antitumor response to paracrine IL-2 in the brain differed significantly from that in the flank, suggesting that the intrinsic CNS cells involved in initiating immunity within the brain have different cytokine requirements from their peripheral counterparts.

Differential T cell response in central and peripheral nerve injury: connection with immune privilege

The central nervous system (CNS), unlike the peripheral nervous system (PNS), is an immune-privileged site in which local immune responses are restricted. Whereas immune privilege in the intact CNS has been studied intensively, little is known about its effects after trauma. In this study, we examined the influence of CNS immune privilege on T cell response to central nerve injury. Immunocytochemistry revealed a significantly greater accumulation of endogenous T cells in the injured rat sciatic nerve than in the injured rat optic nerve (representing PNS and CNS white matter trauma, respectively). Use of the in situ terminal deoxytransferase-catalyzed DNA nick end labeling (TUNEL) procedure revealed extensive death of accumulating T cells in injured CNS nerves as well as in CNS nerves of rats with acute experimental autoimmune encephalomyelitis, but not in injured PNS nerves. Although Fas ligand (FasL) protein was expressed in white matter tissue of both systems, it was more pronounced in the CNS. Expression of major histocompatibility complex (MHC) class II antigens was found to be constitutive in the PNS, but in the CNS was induced only after injury. Our findings suggest that the T cell response to central nerve injury is restricted by the reduced expression of MHC class II antigens, the pronounced FasL expression, and the elimination of infiltrating lymphocytes through cell death.

Innate and adaptive immune responses can be beneficial for CNS repair

The limitation of immune responsiveness in the mammalian CNS has been attributed to the intricate nature of neuronal networks, which would appear to be more susceptible than other tissues to the threat of permanent disorganization when exposed to massive inflammation. This line of logic led to the conclusion that all forms of CNS inflammation would do more harm than good and, hence, the less immune intervention the better. However, mounting evidence indicates that some forms of immune-system intervention can help to protect or restore CNS integrity. We have shown that the innate immune system, represented by activated macrophages, can facilitate the processes of regeneration in the severed spinal cord. More recently, we found that autoimmune T cells that are specific for a component of myelin can protect CNS neurons from the catastrophic secondary degeneration, which extends traumatic lesions to adjacent CNS areas that did not suffer direct damage. The challenge, therefore, is to learn how to modify immune interactions in the traumatized CNS in order to promote its post-injury maintenance and repair.

Interferon beta-1b treatment modulates TNFalpha and IFNgamma spontaneous gene expression in MS

BACKGROUND

Interferon beta (IFNbeta) lessens the overall frequency of acute attacks in patients with the relapsing-remitting form of multiple sclerosis (RRMS). IFNbeta may act by decreasing the synthesis of inflammatory cytokines.

OBJECTIVES

To determine whether IFNbeta-1b treatment had an initial and sustained effect on the in vivo synthesis and secretion of tumor necrosis factor alpha (TNFalpha) and IFNgamma.

METHODS

A highly sensitive reverse-transcriptase PCR technique was used to measure baseline levels of mRNA in freshly isolated cells from patients before therapy and at 3, 6, and 12 months of treatment. Also, protein concentration was measured in serum and in culture supernatants from mitogen-stimulated cells. The authors studied 16 patients, of whom 11 did not have clinical exacerbations, whereas 5 had one clinical relapse each during the study.

RESULTS

Mean values of TNFalpha mRNA levels in the 11 stable patients decreased significantly at 3 and 6 months of treatment in comparison with initial data. After 6 months of therapy, IFNbeta-1b downmodulated TNFalpha transcripts in the 5 patients who experienced relapse. In this group of patients, TNFalpha levels rose sharply to reach pretreated values at 1 year of IFNbeta-1b treatment. At the beginning of therapy, 6 patients had high concentrations of serum TNFalpha, which decreased to normal values following IFNbeta-1b therapy. IFNgamma mRNA expression also diminished after 6 and 12 months of IFNbeta-1b therapy in the group of stable patients, whereas nonrelevant variations were observed in patients who had one relapse. Initially, patients' peripheral mononuclear cells secreted diminished amounts of TNFalpha and IFNgamma on PHA + PMA mitogen stimulation in comparison with normal control subjects. After 1 year of therapy, IFNbeta-1b restored the normal production of TNFalpha, whereas therapy did not restore IFNgamma secretion to control values.

CONCLUSION

IFNbeta-1b decreases the spontaneous expression of two proinflammatory cytokines.

Macrophages/microglial cells in human central nervous system during development: an immunohistochemical study

The development of microglia and macrophages was studied in 14 human embryos and fetuses ranging in age from 4.5-13.5 gestational weeks (g.w.), using lectins, Ricinus communis agglutinin-1 [RCA-1], and Lycopersicon esculentum, tomato lectin (TL), which recognize macrophages and microglia, and antibodies for the macrophage antigen CD68. Lectin-positive (+) cells were observed at 4.5 g.w., the youngest age examined. They were detected in the leptomeninges around the neural tube, and only rarely were observed in the CNS parenchyma. At 5.5 g.w., lectin+ cells were present throughout the CNS parenchyma, and a portion of these cells could also be labeled with antibody to CD68. In subsequent weeks, both types of cells, lectin+ and CD68+/lectin+ cells co-existed and progressively developed typical microglial morphology. In addition, in double label experiments, an antibody that labels CD14 antigen present on monocytes, hematogenous precursors of tissue macrophages, did not label either lectin+ or CD68+/lectin+ cells in CNS parenchyma. Additional immunocytochemical studies with appropriate markers excluded the possibility that any of the cells described here were either astrocytes, oligodendrocytes, endothelial cells or neurons. Our finding that one class of cells can be labeled early only with lectins, while another can be labeled with both lectins and CD68 macrophage antibody, may reflect a different origin of microglia in the early embryonic CNS compared to the fetal stages. This subdivision appears to be maintained in the adult brains as well.

Autoantibodies in neurodegenerative diseases: antigen-specific frequencies and intrathecal analysis

The frequency of autoantibodies (AAbs) was surveyed in several neurodegenerative diseases, other neurological diseases, and controls using antigen-specific EIAs for neurofilament heavy subunit, tubulin, glial fibrillary acidic protein, S100 protein, tau, beta-amyloid peptide, myelin basic protein, and heparan sulfate proteoglycan. High frequencies of sera and cerebrospinal fluid tubulin AAbs were found in Alzheimer disease (62% and 69%, respectively), Parkinson disease (27% and 70%), amyotrophic lateral sclerosis (54% and 67%), and in sera from multiple sclerosis (50% and 67%), optic neuritis (85%), Guillain-Barré syndrome (88%), and vascular dementia (52%). High frequencies of neurofilament heavy subunit AAbs were detected in Guillain-Barré syndrome, chronic peripheral neuropathy (88%) and optic neuritis (62%); whereas, some Alzheimer's disease (33%) and vascular dementia (44%) patients had glial fibrillary acidic protein AAbs. Lower frequencies of other AAbs were found in patient groups. AAb results were also compared to functional assessment of blood-brain barrier integrity in Parkinson's disease and Alzheimer's disease. The relevance of these AAbs to pathogenesis and/or course of neurologic diseases merits further study with particular reference to subgrouping and prognosis.

Intracerebral inflammation after human brain contusion

OBJECTIVE

This study was undertaken to analyze the inflammatory components in contused human brain tissue to compare the findings with previous experimental data regarding the pathogenesis of brain contusions.

METHODS

Contused brain tissue biopsies were obtained from 12 consecutive patients undergoing surgery for brain contusions 3 hours to 5 days after trauma. Inflammatory and immunological components were analyzed by immunohistochemistry.

RESULTS

In patients undergoing surgery less than 24 hours after trauma, the inflammatory response was limited to vascular margination of polymorphonuclear cells. In patients undergoing surgery 3 to 5 days after trauma, however, a massive inflammatory response consisting of monocytes/macrophages, reactive microglia, polymorphonuclear cells, and CD4- and CD8-positive T lymphocytes was detected. Human lymphocyte antigen-DQ was expressed on reactive microglia and infiltrating leukocytes in the late patient group. In addition, CD1a, which is a marker for antigen-presenting dendritic cells, was detected in a subgroup of microglial cells.

CONCLUSION

The results corroborated hypotheses derived from experimental data. In the early phase after contusional trauma, inflammation is mainly intravascular and dominated by polymorphonuclear cells. The inflammation was parenchymal in patients undergoing surgery 3 to 5 days after trauma. The brain swelling seemed to be biphasic, the delayed phase correlating with a parenchymal inflammation. The inflammatory cells may produce several potentially harmful effects, such as acute cellular degeneration; they may also lead to degenerative long-term effects.

A proposed new strategy of immunotherapy for Alzheimer's disease

Current data on the involvement of the immunological system in the pathogenesis of Alzheimer's disease (AD) are discussed, and results of immunotherapy for the disease are provided. Hypotheses on immune aging as a risk factor for AD, and a suggested new treatment strategy, are presented and discussed.

Differential generation of class I H-2D- versus H-2K-restricted cytotoxicity against a demyelinating virus following central nervous system infection

Despite the fact that both H-2K and D molecules are up-regulated in the central nervous system (CNS) following Theiler's murine encephalomyelitis virus (TMEV) infection, resistance in this virus model of multiple sclerosis maps exclusively to D. To address this paradox, we examined the ability of the K and D molecules to present viral antigens to cytotoxic T lymphocytes (CTL). Whereas no virus-specific CTL were detected in the CNS of susceptible B10.Q and B10.S mice 7 days post-infection, D-restricted CTL were identified readily in the CNS of resistant B10 animals. There was no evidence of K-restricted CTL in the CNS of B10 mice at day 7 post-infection. The presence of both K- and D-restricted virus-specific CTL in the spleen of immunized B10 mice demonstrates that the exclusive use of D molecules by CTL in the CNS of mice 7 days post-infection is not due to the inability of the K molecules to present viral peptides to lymphocytes. We conclude that the prominent role of the D locus in determining resistance or susceptibility to TMEV-induced demyelination is determined by factors governing the regulation of the immune response, and not by the presence or absence of CTL precursors capable of recognizing viral peptides presented by the K and D antigen-presenting molecules, or by differences in the ability of the K and D molecules to present viral peptides.

[Genetic aspects in multiple sclerosis. II: HLA system]

Review of studies about HLA antigens and multiple sclerosis (MS). The HLA system, in special class II antigens, subregions DR and DQ, is probably involved in the immunopathogenesis of MS. Haplotype DRB1*1501.DQA1*0102.DQB1*0602, corresponding to phenotype DR2.Dw2.DQ6, is positively associated with MS in several caucasoid populations. Clinical heterogeneity of MS, as well as different diagnostic criteria adopted by investigators are potential sources of confusion and may lead to discrepant results. A better standardization of clinical and laboratorial methodology, appropriate subdivision of patients with different clinical forms of MS, may allow a more accurate evaluation of the role of genetic factors in the pathogenesis of MS.

Onconeural antigens and the paraneoplastic neurologic disorders: at the intersection of cancer, immunity, and the brain

Paraneoplastic neurologic disorders (PNDs) are believed to be autoimmune neuronal degenerations that develop in some patients with systemic cancer. A series of genes encoding previously undiscovered neuronal proteins have been cloned using antiserum from PND patients. Identification of these onconeural antigens suggests a reclassification of the disorders into four groups: those in which neuromuscular junction proteins, nerve terminal/vesicle-associated proteins, neuronal RNA binding proteins, or neuronal signal-transduction proteins serve as target antigens. This review considers insights into basic neurobiology, tumor immunology, and autoimmune neuronal degeneration offered by the characterization of the onconeural antigens.

Inflammation in EAE: role of chemokine/cytokine expression by resident and infiltrating cells

Experimental allergic encephalomyelitis (EAE) is an inflammatory demyelinating disease of the central nervous system (CNS) which has many clinical and pathological features in common with multiple sclerosis (MS). Comparison of the histopathology of EAE and MS reveals a close similarity suggesting that these two diseases share common pathogenetic mechanisms. Immunologic processes are widely accepted to contribute to the initiation and continuation of the diseases and recent studies have indicated that microglia, astrocytes and the infiltrating immune cells have separate roles in the pathogenesis of the MS lesion. The role of cytokines as important regulatory elements in these immune processes has been well established in EAE and the presence of cytokines in cells at the edge of MS lesions has also been observed. However, the role of chemokines in the initial inflammatory process as well as in the unique demyelinating event associated with MS and EAE has only recently been examined. A few studies have detected the transient presence of selected chemokines at the earliest sign of leukocyte infiltration of CNS tissue and have suggested astrocytes as their cellular source. Based on these studies, chemokines have been postulated as a promising target for future therapy of CNS inflammation. This review summarized the events that occur during the inflammatory process in EAE and discusses the roles of cytokine and chemokine expression by the resident and infiltrating cells participating in the process.

Comparative study of the role of professional versus semiprofessional or nonprofessional antigen presenting cells in the rejection of vascularized organ allografts

The immune systems of transplant recipients are progressively challenged with exposure to the multiple lineages of donor cells that comprise the vascularized organ allograft. Each lineage of such donor tissue constitutively expresses or can be induced to express varying densities of MHC antigens ranging from no expression of MHC to MHC class I only to both MHC class I and class II. In addition, the cell surface expression of a diverse assortment of costimulatory and cell adhesion molecules also varies in density in a tissue specific fashion within the allograft. The MHC class I/II molecules displayed on the donor cells contain within their clefts a constellation of processed protein antigens in the form of peptides derived from intracellular and to some extent extracellular sources. Therefore, the potential for each cell lineage to induce alloactivation and serve as a target for allospecific immune responses is dependent on the diversity and density of peptide-bearing MHC molecules, costimulatory molecules, and cell adhesion molecules. In addition, the T cell receptor repertoire of the recipient also contributes to the magnitude of the allogeneic response. Consequently, the variety of clinical outcomes following organ transplantation even with the institution of potent immunosuppressive (drug) therapies is not surprising, as it appears reasonable for such therapies to influence the allogeneic response against distinct lineages differentially. Our failure to prevent chronic human allograft rejection may therefore be due to our limited appreciation of the full spectrum of alloactivating experiences encountered by host T cells as they interact with donor cells of diverse tissue lineages. Investigations by our laboratory of the immunopathogenesis of chronic cardiac allograft rejection have revealed an intrinsic inability of human cardiac myocytes to process and present antigens, not only for primary but also for secondary alloimmune responses. One obvious explanation for this phenomenon is the fact that cardiac myocytes do not constitutively express MHC class II molecules and express only low levels of class I molecules. However, this immunological unresponsiveness is maintained even after the induction of MHC class II and upregulation of MHC class I on these cells by interferon-gamma (IFN-gamma). Similar results have also been reported for cells of different tissue lineages (e.g. chondrocytes, keratinocytes, neural cells). Until now, cells have been defined as professional or nonprofessional for the purposes of defining their potential for antigen presentation to T cells. Professional antigen presenting cells have been identified as cells that are of haematopoietic origin, that constitutively express MHC class I and class II molecules as well as potent costimulatory molecules, and that are able to induce both primary and secondary immune responses, whereas nonprofessional antigen presenting cells are not bone marrow derived, do not constitutively express MHC class II, but may in some cases initiate primary and secondary immune responses after induction of MHC class II antigen by proinflammatory cytokines (e.g. IFN-gamma). The findings of our laboratory and others suggest that cells of certain lineages be considered in the separate class of 'nonantigen presenting cells'. Indeed, nonprofessional antigen presenting cells can be reclassified into three categories: semiprofessional-, nonprofessional-, or nonantigen presenting cells that are able to present antigen to and activate naive T cells, activated T cells, or no T Cells, respectively. The aim of this review is to identify and (re)examine the antigen presentation characteristics of cells of different tissue lineages in terms of their ability to activate different subsets of T cells. This approach is taken in an attempt to synthesize these concepts into a unified picture of T cell activation in the context of antigen processing and presentation by different cell types.