Macrophages regulate induction of delayed-type hypersensitivity and experimental allergic encephalomyelitis in SJL mice

Effects of biological sex and pregnancy in experimental autoimmune encephalomyelitis: It's complicated

Experimental autoimmune encephalomyelitis (EAE) can be induced in many animal strains by inoculation with central nervous system antigens and adjuvant or by the passive transfer of lymphocytes reactive with these antigens and is widely used as an animal model for multiple sclerosis (MS). There are reports that female sex and pregnancy affect EAE. Here we review the effects of biological sex and the effects of pregnancy on the clinical features (including disease susceptibility) and pathophysiology of EAE. We also review reports of the possible mechanisms underlying these differences. These include sex-related differences in the immune system and in the central nervous system, the effects of hormones and the sex chromosomes and molecules unique to pregnancy. We also review sex differences in the response to factors that can modify the course of EAE. Our conclusion is that the effects of biological sex in EAE vary amongst animal models and should not be widely extrapolated. In EAE, it is therefore essential that studies looking at the effects of biological sex or pregnancy give full information about the model that is used (i.e. animal strain, sex, the inducing antigen, timing of EAE induction in relation to pregnancy, etc.). In addition, it would be preferable if more than one EAE model were used, to show if any observed effects are generalizable. This is clearly a field that requires further work. However, understanding of the mechanisms of sex differences could lead to greater understanding of EAE, and suggest possible therapies for MS.

The influence and impact of ageing and immunosenescence (ISC) on adaptive immunity during multiple sclerosis (MS) and the animal counterpart experimental autoimmune encephalomyelitis (EAE)

The human ageing process encompasses mechanisms that effect a decline in homeostasis with increased susceptibility to disease and the development of chronic life-threatening illness. Increasing age affects the immune system which undergoes a progressive loss of efficiency, termed immunosenescence (ISC), to impact on quantitative and functional aspects of innate and adaptive immunity. The human demyelinating disease multiple sclerosis (MS) and the corresponding animal model experimental autoimmune encephalomyelitis (EAE) are strongly governed by immunological events that primarily involve the adaptive arm of the immune response. MS and EAE are frequently characterised by a chronic pathology and a protracted disease course which thereby creates the potential for exposure to the inherent, on-going effects and consequences of ISC. Collective evidence is presented to confirm the occurrence of established and unendorsed biological markers of ISC during the development of both diseases. Moreover, results are discussed from studies during the course of MS and EAE that reveal a premature upregulation of ISC-related biomarkers which indicates untimely alterations to the adaptive immune system. The effects of ISC and a prematurely aged immune system on autoimmune-associated neurodegenerative conditions such as MS and EAE are largely unknown but current evaluation of data justifies and encourages further investigation.

The enteric nervous system is a potential autoimmune target in multiple sclerosis

Multiple sclerosis (MS) is a chronic autoimmune disease of the central nervous system (CNS) in young adults that has serious negative socioeconomic effects. In addition to symptoms caused by CNS pathology, the majority of MS patients frequently exhibit gastrointestinal dysfunction, which was previously either explained by the presence of spinal cord lesions or not directly linked to the autoimmune etiology of the disease. Here, we studied the enteric nervous system (ENS) in a B cell- and antibody-dependent mouse model of MS by immunohistochemistry and electron microscopy at different stages of the disease. ENS degeneration was evident prior to the development of CNS lesions and the onset of neurological deficits in mice. The pathology was antibody mediated and caused a significant decrease in gastrointestinal motility, which was associated with ENS gliosis and neuronal loss. We identified autoantibodies against four potential target antigens derived from enteric glia and/or neurons by immunoprecipitation and mass spectrometry. Antibodies against three of the target antigens were also present in the plasma of MS patients as confirmed by ELISA. The analysis of human colon resectates provided evidence of gliosis and ENS degeneration in MS patients compared to non-MS controls. For the first time, this study establishes a pathomechanistic link between the well-established autoimmune attack on the CNS and ENS pathology in MS, which might provide a paradigm shift in our current understanding of the immunopathogenesis of the disease with broad diagnostic and therapeutic implications.

Resolution of acute inflammation bridges the gap between innate and adaptive immunity

Acute inflammation is traditionally characterized by polymorphonuclear leukocytes (PMN) influx followed by phagocytosing macrophage (Mφs) that clear injurious stimuli leading to resolution and tissue homeostasis. However, using the peritoneal cavity, we found that although innate immune-mediated responses to low-dose zymosan or bacteria resolve within days, these stimuli, but not hyperinflammatory stimuli, trigger a previously overlooked second wave of leukocyte influx into tissues that persists for weeks. These cells comprise distinct populations of tissue-resident Mφs (resMφs), Ly6c(hi) monocyte-derived Mφs (moMφs), monocyte-derived dendritic cells (moDCs), and myeloid-derived suppressor cells (MDSCs). Postresolution mononuclear phagocytes were observed alongside lymph node expansion and increased numbers of blood and peritoneal memory T and B lymphocytes. The resMφs and moMφs triggered FoxP3 expression within CD4 cells, whereas moDCs drive T-cell proliferation. The resMφs preferentially clear apoptotic PMNs and migrate to lymph nodes to bring about their contraction in an inducible nitric oxide synthase-dependent manner. Finally, moMφs remain in tissues for months postresolution, alongside altered numbers of T cells collectively dictating the magnitude of subsequent acute inflammatory reactions. These data challenge the prevailing idea that resolution leads back to homeostasis and asserts that resolution acts as a bridge between innate and adaptive immunity, as well as tissue reprogramming.

Determinants of central nervous system adult neurogenesis are sex, hormones, mouse strain, age, and brain region

Multiple sclerosis is a sexually dimorphic (SD) disease that causes oligodendrocyte death, but SD of glial cells is poorly studied. Here, we analyze SD of neural progenitors in 6-8 weeks and 6-8 months normal C57BL/6, SJL/J, and BALB/c mice in the subventricular zone (SVZ), dorsolateral horn (DLC), corpus callosum (CC), and parenchyma. With a short 2-h bromodeoxyuridine (BrdU) pulse, no gender and strain differences are present at 6-8 weeks. At 6-8 months, the number of BrdU(+) cells decreases twofold in each sex, strain, and region, indicating that a common aging mechanism regulates BrdU incorporation. Strikingly, 2× more BrdU(+) cells are found in all brain regions in 6-8 months C57BL/6 females versus males, no gender differences in 6-8 months SJL/J, and fewer BrdU(+) cells in females versus males in BALB/cs. The number of BrdU(+) cells modestly fluctuates throughout the estrous cycle in C57BL/6 and SJLs. Castration causes a dramatic increase in BrdU(+) cells in SVZ and DLC. These findings indicate that testosterone is a major regulator of adult neural proliferation. At 6-8 months, the ratio of PDGFRα(+) cells in the CC to BrdU(+) cells in the DLC of both strains, sexes, estrous cycle, and castrated mice was essentially the same, suggesting that BrdU(+) cells in the DLC differentiate into CC oligodendrocytes. The ratio of TUNEL(+) to BrdU(+) cells does not match proliferation, indicating that these events are differentially regulated. Differential regulation of these two processes leads to the variation in glial numbers between gender and strain. Explanations of neural proliferation based upon data from one sex or strain may be very misleading.

The dual roles of inflammatory cytokines and chemokines in the regulation of autoimmune diseases and their clinical implications

Cytokines and chemokines are secreted, small cell-signaling protein molecules, whose receptors are expressed on immune cells. These factors play a critical role in immune cell differentiation, migration, and polarization into functional subtypes and in directing their biological functions. Much attention has been devoted to exploring the role of key inflammatory cytokines and promigratory chemokines in autoimmune, autoinflammatory, and allergic diseases, leading to development of therapeutic strategies that are based on their targeted neutralization. Recent studies, including those coming from our groups, show that several major proinflammatory cytokines and chemokines, including IFN-γ, IL-2, CCL2, and CXCL12, may also function as anti-inflammatory mediators and therefore, may have potential as anti-inflammatory drugs. Likewise, major anti-inflammatory mediators, such as TGF-β, may under certain conditions, in combination with other cytokines, exhibit proinflammatory function and direct the polarization of the highly inflammatory CD4(+) Th17 cells. We show here that the biological function of pro- and anti-inflammatory cytokines is dependent on three key parameters: the local concentration of a given cytokine, the stage of disease in which it is administered, and its combination with other cytokines. The therapeutic implications of these findings are discussed, including two very recent studies summarizing clinical trials, in which low-dose administration of IL-2 was used to successfully suppress HCV and GVHD.

Peritoneal macrophage from male and female SJL mice differ in IL-10 expression and macrophage maturation

Injection of proteins and particulate antigens into the peritoneal cavity of male SJL mice preferentially activates T cells secreting Th2 cytokines. Identical immunizations of females activate T cells secreting Th1 cytokines. CD11b(+)F4/80(hi) LPM and CD11b(+)F4/80(lo) SPM populations were compared between naive males and females to define their role in supporting differential Th1 versus Th2 T cell activation. No sex-dependent differences in the expression of MHC class II, costimulatory molecules, and MR were detected. Immunization induced influx of CD11b(lo)F4/80(lo) cells in both sexes. CD11b(lo)F4/80(lo) cells consist predominantly of Ly6C(hi) monocytes, which mature into a Ly6C(-) SPM subset. Following immunization, equivalent frequencies of LPM had taken up antigen. However, the CD11b(lo)F4/80(lo) population, which had taken up antigen, was decreased significantly in males compared with females. Similar to naïve macrophages, antigen-positive cells in immunized males and females exhibited no phenotypic differences. However, fewer Ly6C(-)F4/80(+) cells were present in males compared with females, consistent with the reduced number of antigen-positive cells. Furthermore, CD11b(lo)F4/80(lo) cells, which had taken up antigen in males, expressed increased IL-10 and limited IL-12 mRNA compared with the predominant IL-12 mRNA expression in female-derived, antigen-positive CD11b(lo)F4/80(lo) cells. IL-10 blockade increased the frequency of Ly6C(-)F4/80(+) cells in males to the frequency in females, suggesting that preferential activation of Th2 T cells in male SJL mice is associated with increased IL-10 expression and limited antigen presentation as a result of decreased macrophage maturation under the influence of IL-10.

Praziquantel facilitates IFN-γ-producing CD8+ T cells (Tc1) and IL-17-producing CD8+ T cells (Tc17) responses to DNA vaccination in mice

Background

CD8⁺ cytotoxic T lymphocytes (CTLs) are crucial for eliminating hepatitis B virus (HBV) infected cells. DNA vaccination, a novel therapeutic strategy for chronic virus infection, has been shown to induce CTL responses. However, accumulated data have shown that CTLs could not be effectively induced by HBV DNA vaccination.

Methodology/Principal Findings

Here, we report that praziquantel (PZQ), an anti-schistoma drug, could act as an adjuvant to overcome the lack of potent CTL responses by HBV DNA vaccination in mice. PZQ in combination with HBV DNA vaccination augmented the induction of CD8⁺ T cell-dependent and HBV-specific delayed hypersensitivity responses (DTH) in C57BL/6 mice. Furthermore, the induced CD8⁺ T cells consisted of both Tc1 and Tc17 subtypes. By using IFN-γ knockout (KO) mice and IL-17 KO mice, both cytokines were found to be involved in the DTH. The relevance of these findings to HBV immunization was established in HBsAg transgenic mice, in which PZQ also augmented the induction of HBV-specific Tc1 and Tc17 cells and resulted in reduction of HBsAg positive hepatocytes. Adoptive transfer experiments further showed that PZQ-primed CD8⁺ T cells from wild type mice, but not the counterpart from IFN-γ KO or IL-17 KO mice, resulted in elimination of HBsAg positive hepatocytes.

Conclusions/Significance

Our results suggest that PZQ is an effective adjuvant to facilitate Tc1 and Tc17 responses to HBV DNA vaccination, inducing broad CD8⁺ T cell-based immunotherapy that breaks tolerance to HBsAg.

Increased T regulatory cells lead to development of Th2 immune response in male SJL mice

SJL mice represent a mouse model in which young adult females are susceptible to autoimmune disease, while age-matched males are relatively resistant. T cells primed in female SJL mice secrete cytokines associated with a Th1 phenotype. By contrast, T cells primed in males secrete cytokines associated with a Th2 phenotype. Activation of Th2-type T cells in males vs. Th1 cells in females correlates with increased CD4(+)CD25(+) T regulatory cells (Treg) in males. T cells primed in males depleted of CD4(+)CD25(+) T cells preferentially secrete IFN-γ and decreased IL-4 and IL-10 compared to CD4(+)CD25(+) T-cell-sufficient males, suggesting that Treg influence subsequent antigen-specific cytokine secretion. Treg from males and females exhibit equivalent in vitro T-cell suppression. Treg from males express increased CTLA-4 and CD62L and preferentially secrete IL-10. These data suggest that an increased frequency of IL-10 secreting Treg in male SJL mice may contribute resistance to autoimmune disease by favoring the development of Th2 immune responses.

Central neuroinvasion and demyelination by inflammatory macrophages after peripheral virus infection is controlled by SHP-1

SHP-1 is a protein tyrosine phosphatase that negatively regulates cytokine signaling and inflammatory gene expression. Mice genetically lacking SHP-1 (me/me) display severe inflammatory demyelinating disease following intracranial inoculation with the BeAn strain of Theiler's murine encephalomyelitis virus (TMEV) compared to infected wild-type mice. Furthermore, SHP-1-deficient mice show a profound and predominant infiltration of blood-derived macrophages into the CNS following intracerebral injection of TMEV, and these macrophages are concentrated in areas of demyelination in brain and spinal cord. In the present study we investigated the role of SHP-1 in controlling CNS inflammatory demyelination following a peripheral instead of an intracerebral inoculation of TMEV. Surprisingly, we found that while wild-type mice were entirely refractory to intraperitoneal (IP) infection by TMEV, in agreement with previous studies, all SHP-1-deficient mice displayed profound macrophage neuroinvasion and macrophage-mediated inflammatory demyelination. Moreover, SHP-1 deficiency led to increased expression of inflammatory molecules in macrophages, serum, and CNS following IP infection with TMEV. Importantly, pharmacological depletion of peripheral macrophages significantly decreased both paralysis and CNS viral loads in SHP-1-deficient mice. In addition, peripheral MCP-1 neutralization attenuated disease severity, decreased macrophage infiltration into the CNS, and decreased monocyte numbers in the blood of SHP-1-deficient mice, implicating MCP-1 as an important mediator of monocyte migration between multiple tissues. These results demonstrate that peripheral TMEV infection results in a unique evolution of macrophage-mediated demyelination in SHP-1-deficient mice, implicating SHP-1 in the control of neuroinvasion of inflammatory macrophages and neurotropic viruses into the CNS.

Cutting edge: the Y chromosome controls the age-dependent experimental allergic encephalomyelitis sexual dimorphism in SJL/J mice

Multiple sclerosis is a sexually dimorphic, demyelinating disease of the CNS, and experimental allergic encephalomyelitis (EAE) is its principal autoimmune model. Young male SJL/J mice are relatively resistant to EAE whereas older males and SJL/J females of any age are susceptible. By comparing a wide age range of proteolipid protein peptide 139-151 immunized mice, we found that female disease severity remains constant with age. In contrast, EAE disease severity increases with age in SJL/J males, with young males having significantly less severe disease and older males having significantly more disease than equivalently aged females. To determine whether the Y chromosome contributes to this sexual dimorphism, EAE was induced in consomic SJL/J mice carrying a B10.S Y chromosome (SJL.Y(B10.S)). EAE was significantly more severe in young male SJL.Y(B10.S) mice compared with young male SJL/J mice. These studies show that a Y chromosome-linked polymorphism controls the age-dependent EAE sexual dimorphism observed in SJL/J mice.

Inhibition of experimental autoimmune encephalomyelitis by a novel small molecular weight proinflammatory cytokine suppressing drug

Experimental autoimmune encephalomyelitis (EAE) is a T cell-mediated, autoimmune disease of the central nervous system (CNS) that serves as a model for various cellular and molecular aspects of the human disease, multiple sclerosis (MS). Although EAE has long been considered a T cell-mediated disease, macrophages play a role in disease pathogenesis and are known to accumulate in the CNS under the control of chemokines. In the present report we demonstrate that mice induced to develop EAE were treated with a small molecular weight molecule that suppresses proinflammatory cytokine production which resulted in significantly decreased clinical EAE, CNS CCL2 expression and CNS macrophage accumulation. These results demonstrate the efficacy of a novel class of therapeutic molecules for CNS demyelinating disease.

Modulation of macrophage infiltration and inflammatory activity by the phosphatase SHP-1 in virus-induced demyelinating disease

The protein tyrosine phosphatase SHP-1 is a crucial negative regulator of cytokine signaling and inflammatory gene expression, both in the immune system and in the central nervous system (CNS). Mice genetically lacking SHP-1 (me/me) display severe inflammatory demyelinating disease following inoculation with the Theiler's murine encephalomyelitis virus (TMEV) compared to infected wild-type mice. Therefore, it became essential to investigate the mechanisms of TMEV-induced inflammation in the CNS of SHP-1-deficient mice. Herein, we show that the expression of several genes relevant to inflammatory demyelination in the CNS of infected me/me mice is elevated compared to that in wild-type mice. Furthermore, SHP-1 deficiency led to an abundant and exclusive increase in the infiltration of high-level-CD45-expressing (CD45(hi)) CD11b(+) Ly-6C(hi) macrophages into the CNS of me/me mice, in concert with the development of paralysis. Histological analyses of spinal cords revealed the localization of these macrophages to extensive inflammatory demyelinating lesions in infected SHP-1-deficient mice. Sorted populations of CNS-infiltrating macrophages from infected me/me mice showed increased amounts of viral RNA and an enhanced inflammatory profile compared to wild-type macrophages. Importantly, the application of clodronate liposomes effectively depleted splenic and CNS-infiltrating macrophages and significantly delayed the onset of TMEV-induced paralysis. Furthermore, macrophage depletion resulted in lower viral loads and lower levels of inflammatory gene expression and demyelination in the spinal cords of me/me mice. Finally, me/me macrophages were more responsive than wild-type macrophages to chemoattractive stimuli secreted by me/me glial cells, indicating a mechanism for the increased numbers of infiltrating macrophages seen in the CNS of me/me mice. Taken together, these findings demonstrate that infiltrating macrophages in SHP-1-deficient mice play a crucial role in promoting viral replication by providing abundant viral targets and contribute to increased proinflammatory gene expression relevant to the effector mechanisms of macrophage-mediated demyelination.

Production of CCL2 by central nervous system cells regulates development of murine experimental autoimmune encephalomyelitis through the recruitment of TNF- and iNOS-expressing macrophages and myeloid dendritic cells

Experimental autoimmune encephalomyelitis is a T cell-mediated demyelinating disease of the CNS that serves as a model for the human disease multiple sclerosis. Increased expression of the chemokine CCL2 in the CNS has been demonstrated to be important in the development of demyelinating disease presumably by attracting inflammatory cells. However, the mechanism of how CCL2 regulates disease pathogenesis has not been fully elucidated. Using radiation bone marrow chimeric mice we demonstrated that optimum disease was achieved when CCL2 was glia derived. Furthermore, CNS production of CCL2 resulted in the accumulation of iNOS-producing CD11b(+)CD11c(+) dendritic cells and TNF-producing macrophages important for demyelination. Lack of glial-derived CCL2 production did not influence experimental autoimmune encephalomyelitis by altering either Th1 or Th17 cells, as there were no differences in these populations in the CNS or periphery between groups. These results demonstrate that the glial-derived CCL2 is important for the attraction of TNF- and iNOS-producing dendritic cells and effector macrophages to the CNS for development of subsequent autoimmune disease.

The contribution of nitric oxide and interferon gamma to the regulation of the neuro-inflammation in experimental autoimmune encephalomyelitis

Nitric oxide (NO) is a key messenger involved in physiological functions including endothelium-dependent vascular relaxation, inhibition of platelet adhesion and aggregation and regulation of inflammatory and immune responses. Here we briefly introduce NO and its functions and then describe our work over the past several years examining the role of NO in EAE in both the rat and the mouse. We show that NO plays a significant role in determining the resistance or susceptibility to EAE in various strains and or sexes of animals. We demonstrate that NO down-regulates several aspects of CNS inflammation but also has a dual role in that it is required for inflammation in some situations.

Soluble mannosylated myelin peptide inhibits the encephalitogenicity of autoreactive T cells during experimental autoimmune encephalomyelitis

We have previously shown that immunization with a mannosylated myelin peptide in complete adjuvant induces tolerance instead of disease in experimental autoimmune encephalomyelitis (EAE), a rodent model for multiple sclerosis. In this report we demonstrate that treatment with a soluble mannosylated epitope of proteolipid protein (M-PLP(139-151)) significantly inhibits disease mediated by autoreactive myelin-specific T cells during EAE. Treatment with M-PLP(139-151), applied in different EAE models, significantly reduced the incidence of disease and the severity of clinical symptoms. Delayed-type hypersensitivity responses were abolished after peptide treatment, emphasizing the impact on peripheral T-cell reactivity. Histological analysis of spinal cord tissue from mice treated with M-PLP(139-151) revealed the presence of only few macrophages and T cells. Moreover, little expression of interferon-gamma, interleukin-23, or major histocompatibility complex class II antigen was detected. Immune modulation by M-PLP(139-151) was primarily antigen-specific because an irrelevant mannosylated peptide showed no significant effect on delayed-type hypersensitivity responses or on the course of EAE. Therefore, mannosylated antigens may represent a novel therapeutic approach for antigen-specific modulation of autoreactive T cells in vivo.

TRPV1+ sensory neurons control beta cell stress and islet inflammation in autoimmune diabetes

In type 1 diabetes, T cell-mediated death of pancreatic beta cells produces insulin deficiency. However, what attracts or restricts broadly autoreactive lymphocyte pools to the pancreas remains unclear. We report that TRPV1(+) pancreatic sensory neurons control islet inflammation and insulin resistance. Eliminating these neurons in diabetes-prone NOD mice prevents insulitis and diabetes, despite systemic persistence of pathogenic T cell pools. Insulin resistance and beta cell stress of prediabetic NOD mice are prevented when TRPV1(+) neurons are eliminated. TRPV1(NOD), localized to the Idd4.1 diabetes-risk locus, is a hypofunctional mutant, mediating depressed neurogenic inflammation. Delivering the neuropeptide substance P by intra-arterial injection into the NOD pancreas reverses abnormal insulin resistance, insulitis, and diabetes for weeks. Concordantly, insulin sensitivity is enhanced in trpv1(-/-) mice, whereas insulitis/diabetes-resistant NODxB6Idd4-congenic mice, carrying wild-type TRPV1, show restored TRPV1 function and insulin sensitivity. Our data uncover a fundamental role for insulin-responsive TRPV1(+) sensory neurons in beta cell function and diabetes pathoetiology.

Nitric oxide contributes to the resistance of young SJL/J mice to experimental autoimmune encephalomyelitis

EAE development in SJL/J mice is age and sex dependent: young males are EAE resistant; females and adult males are EAE susceptible. By studying splenocytes' IFNgamma and NO production and the induction or the suppression of actively induced EAE by manipulating NO systemic levels, we provide evidence that the failure of young male SJL/J mice to develop EAE lies in the activation of the innate immune system by the immunising stimulus.

Impact of macrophage and dendritic cell subset elimination on antiviral immunity, viral clearance and production of type 1 interferon

We report herein that vesicular stomatitis virus (VSV) induced a concurrent primary Th1 (T helper 1) and Th2 cytokine response detectable ex vivo. Liposome-encapsulated clodronate-mediated elimination of CD8- marginal dendritic cells (DCs) and splenic macrophages (m Phi), but not CD8+ interdigitating DCs, prior to infection resulted in a markedly diminished chemokine and Th1 (IL-2, interferon-gamma) cytokine response, although the Th2 response (IL-4) remained relatively intact. Repopulation with marginal DCs and marginal metallophilic macrophages (MMM) restored Th1 cytokine profiles but did not restore chemokine responsiveness or reduce VSV-induced morbidity/mortality. Chemokine competency returned approximately 4 weeks post-depletion, which correlated temporally with repopulation of the spleen with marginal zone macrophages (MZM) and red pulp macrophages (RPM). Unexpectedly, virus-induced morbidity persisted for over 1 month post-depletion and was associated with virus dissemination and distinctive histological lesions in the liver. Depletion of interferon-producing plasmacytoid dendritic cells did not account for virus-induced morbidity because serum levels of type I interferon were not diminished in Cl2MBP-liposome-treated mice. Thus, distinct m Phi subsets are critical for chemokine production and viral clearance, and, in their absence, VSV disseminates even in the presence of high titers of interferon.

Targeted overexpression of IL-18 binding protein at the central nervous system overrides flexibility in functional polarization of antigen-specific Th2 cells

The current study shows that functional polarization of Ag-specific CD4(+) Th2 cells entering the CNS during the accelerating phase of experimental autoimmune encephalomyelitis is flexible and dependent on the cytokine milieu there. Thus, targeted cell/gene therapy by Ag-specific T cells overexpressing IL-18 binding protein overrides this flexibility and induces infectious spread of T cell tolerance. Using a congenic system, we demonstrated that at this time, Ag-specific Th2 cells accumulate at the CNS but then arrest of IL-4 production. A manipulation of targeted cell/gene delivery was then used to detect whether this function is dependent on the cytokine milieu there. Targeted overexpression of IL-18 binding protein, a natural inhibitor of IL-18, restored the ability of these Ag-specific Th2 cells to produce IL-4 and subsequently induce protective spread of Th2 polarization. These findings not only suggest a novel way of therapy, but also explain why shifting the balance of Ag-specific T cells toward Th2 suppresses ongoing experimental autoimmune encephalomyelitis, whereas a direct transfer of these cells is ineffective.

Oral testosterone in male rats and the development of experimental autoimmune encephalomyelitis

OBJECTIVES

Considering that sex steroids can influence the immune system, we studied the development of experimental autoimmune encephalomyelitis (EAE), a T-cell-mediated autoimmune disease of the central nervous system, and the concomitant cell-mediated immunity in gonadally intact and gonadectomized male Wistar rats given testosterone supplementation.

METHODS/RESULTS

Sham-operated rats and surgically castrated animals were orally self-administered with vehicle or testosterone added in the water bottle for 20 days before EAE induction. The androgenic effect of oral testosterone self-administration was evidenced by changes in body weight, and in the weights of androgen-dependent testes and seminal vesicles. Testosterone administration reduced the incidence of clinical signs of EAE in sham-operated animals and reversed the clinical symptoms of the disease associated with castrated EAE animals. The clinical signs observed in the different groups correlated with changes in delayed-type hypersensitivity and mononuclear cell-proliferative responses to the encephalitogenic myelin basic protein. Moreover, testosterone but not cholesterol supplementation in vitro suppressed the proliferative response of mononuclear cells to myelin basic protein suggesting that testosterone may affect specific immune functions through direct actions on immune cells. Finally, self-administration of testosterone induced also elevated corticosterone levels that in sham-operated rats correlated with the low incidence of the disease and in gonadectomized animals could be involved in the remission of clinical symptoms of EAE.

CONCLUSIONS

These results suggest that orally self-administered testosterone can modulate specific cellular immune responses and serum corticosterone levels leading to changes in the development of EAE.

Gender, age, and season at immunization uniquely influence the genetic control of susceptibility to histopathological lesions and clinical signs of experimental allergic encephalomyelitis: implications for the genetics of multiple sclerosis

Multiple sclerosis (MS), the principal inflammatory demyelinating disease of the central nervous system (CNS), is believed to have an immunopathological etiology arising from gene-environment interactions. In this study, we examined the effect of sex, age, and season at immunization on the susceptibility of (B10.S x SJL/J) F(2) intercross mice to experimental allergic encephalomyelitis (EAE), the foremost animal model of MS. Results of logistic regression analyses suggest that female mice were more likely to exhibit CNS lesions than male mice [odds ratio (OR) = 2.28 for brain lesions; OR = 2.37 for spinal cord (SC) lesions]. Although statistically significant associations were seen between brain and SC lesions and age at the time of injection or month of injection when examined separately; these associations disappeared when controlling for sex in multiple logistic regression analyses. These results suggest that the sex of the mouse is more important in influencing the development of brain and SC lesions than was either age or month of immunization. When examining clinical disease as the endpoint, the OR for the age at immunization is 1.04, indicating that the odds of being affected increase by 4% for each increasing week of age. When controlled for age, the OR for injection in the summer months (July through September) is 1.90, suggesting that the odds of being clinically affected are 90% greater for F(2) intercross animals injected in the summercompared to those injected in the winter to spring months (February through May). In contrast to CNS lesions, the age and season at immunization significantly and independently influenced susceptibility to clinical EAE and did so equally in both males and females. Linkage analysis to eae5, the H2-linked locus controlling susceptibility to clinical disease, was performed using 6- to 12- and >12-week-old cohorts as well as summer and winter/spring cohorts of F(2) mice. Significant linkage of clinical EAE to eae5 was observed with the 6- to 12-week-old and summer populations. In contrast, linkage of clinical EAE to eae5 was not detected with the >12-week-old and winter/spring populations. These results indicate that age and seasonal effects are capable of overriding eae5-dependent genetic control of susceptibility to clinical EAE and have significant implications for the genetics of MS.

Sex differences in experimental autoimmune encephalomyelitis in multiple murine strains

Multiple sclerosis (MS) is more prevalent in women than men. We evaluated seven different mouse strains commonly used in the study of autoimmune diseases, for sex differences in the disease course of experimental autoimmune encephalomyelitis (EAE). Greater severity of EAE was observed in the female SJL immunized with two different peptides of myelin proteolipid protein (PLP) and myelin oligodendrocyte glycoprotein (MOG) as well as in the female ASW relative to males. Female NZW mice showed a greater incidence of EAE than males. However, male B10.PL and PL/J mice showed more severe disease than females. No sex differences were noted in the C57BL/6 or NOD strains.

Suppression of Ongoing Adjuvant-Induced Arthritis by Neutralizing the Function of the p28 Subunit of IL-27

IL-27 is a recently defined family member of the long-chain four-helix bundle cytokines, which consists of EBI3, an IL-12p40-related protein, and p28, an IL-12p35-related polypeptide. The role of IL-27 in the regulation of inflammatory autoimmune diseases has never been studied. The current study uses the DNA vaccination technology, and highly specific Abs to the p28 subunit of IL-27 that were generated by this technology, to delineate its role in the regulation of adjuvant-induced arthritis in Lewis rats. Neutralizing the in vivo function of IL-27 by targeted DNA vaccines and by Abs against IL-27 p28 that were produced in protected donors could rapidly suppress an ongoing disease. Disease suppression was associated with a reduced ex vivo production of inflammatory cytokines. We then used these Abs to investigate the mechanistic basis of disease suppression, showing that IL-27 is not only involved in directing the polarization of naive T cells, but also affects the proliferative response and cytokine production of Ag-specific effector/memory Th1 cells. This may explain, in part, its important role in the regulation of inflammatory autoimmune diseases, and also suggest novel ways of therapy.

Adult gonadal hormones selectively regulate sexually dimorphic quantitative traits observed in experimental allergic encephalomyelitis

Experimental allergic encephalomyelitis (EAE) and multiple sclerosis (MS) are characterized by strong sexual dimorphisms, many of which may be due to genetically controlled sex hormone effects on the immune system, the central nervous system (CNS), or both. In the present study we used 487 gonadectomized and 376 intact age-matched F(2) mice generated through crosses of B10.S/SgMcdJ and SJL/J mice to assess the role of adult gonadal hormones in regulating clinical and histopathological quantitative traits (QT) associated with EAE in the context of genetic heterogeneity. We found that gonadectomy resulted in different effects, depending on the QT and the sex of the mouse. Ovariectomized mice on average had lower cumulative clinical disease scores, shorter duration of clinical signs, and increased peak disease scores. This trend was accompanied by a significant increase in the incidence of acute, progressive EAE which is more frequently seen in intact and orchiectomized males. Although spinal cord (SC) inflammation was the better predictor of clinical signs of EAE in both sexes, ovariectomized females had considerable reductions in nearly all histopathological QT in both the brain and SC. Orchiectomy resulted in modestly significant increases in disease severity and peak score and earlier onset of clinical signs. With the exception of SC demyelination and lesion scores, orchiectomy had no effect on histopathological QT. Importantly, gonadectomy reduced but did not completely abolish any of the sexually dimorphic clinical QT seen in intact mice. It did however, lead to a significant sexual dimorphism in incidence and severity not seen in intact mice. For histopathological QT, no sexual dimorphism was detected for brain lesions in either intact or gonadectomized mice. In contrast, SC histopathological QT exhibited significant sexual dimorphisms, which were impacted by gonadectomy. The results from this study indicate that within the context of genetic heterogeneity, circulating gonadal hormones influence both clinical and histopathological QT in this model of MS, but they do not solely account for the sexual dimorphisms seen in these traits. Thus, additional mechanisms must play a role in regulating gender differences in autoimmune disease of the CNS.

Immunoregulatory role of ocular macrophages: the macrophages produce RANTES to suppress experimental autoimmune uveitis

Murine experimental autoimmune uveitis (EAU) is a model of human uveitis. Ocular-infiltrating macrophages play a crucial role in the generation of tissue damage in EAU. In fact, several chemokines are actually produced in the inflamed eye. The aim of this study was to elucidate the role of ocular macrophage-derived chemokines in EAU. C57BL/6 mice were immunized with human interphotoreceptor retinoid binding protein peptide 1-20, and the EAU severity was scored at multiple time points based on microscopic fundus observations (retinal vascular dilatation and exudates) and histological examinations. The peak inflammatory response was observed 1 wk (day 16) after the beginning of macrophage infiltration to the eye (day 9). Ocular-infiltrating cells were enriched or depleted of macrophages by magnetic beads and analyzed by real-time RT-PCR for chemokine mRNA production. We found that only the macrophage-enriched cells from the eye produced RANTES, and thus proposed that macrophage-derived RANTES facilitated the ocular inflammations. In contrast to our postulate, neutralization of RANTES by specific Ab in vivo on days 9 and 13 exacerbated EAU. We also found that the ratio of ocular CD4/CD8 T cells was markedly increased after treatment. As a result, RANTES neutralization might exacerbate EAU by modulating the type of T cell subsets recruited to the eye. In conclusion, our data provide insight into the immunoregulatory role of macrophages and RANTES in the pathogenesis of ocular inflammation. Not all macrophage-derived chemokines cause local inflammation, since RANTES produced by ocular macrophages appears to suppress EAU.

NK cells regulate CD4 responses prior to antigen encounter

NK cells not only respond rapidly to infection, shaping subsequent adaptive immunity, but also play a role in regulating autoimmune disease. The ability of NK cells to influence adaptive immunity before Ag exposure was examined in a gender-dependent model of preferential Th1 and Th2 activation. The inability of young adult male SJL mice to activate Th1 cells was reversed via depletion of NK1.1(+) cells, whereas the presence or the absence of NK1.1(+) cells did not alter responses in age-matched females. Consistent with a gender-dependent role in regulating adaptive immunity, significantly more NK1.1(+) cells were present in males compared with females, and this difference was reversed by castration. In contrast to NK1.1(+) cells derived from C57BL/6 mice, no spontaneous cytokine secretion was detected in NK1.1(+) cells derived from either male or female SJL mice, although an increased frequency of IL-10-secreting NK1.1(+) cells was observed in males vs females following in vitro stimulation. Direct evidence that NK1.1(+) cells in males influence CD4(+) T cell activation before Ag exposure was demonstrated via the adoptive transfer of APC from control and NK1.1-depleted males. The absence of a functional NK T cell population in SJL mice suggests that NK cells influence adaptive immunity before Ag exposure via alterations in APC activity.

Susceptibility to T cell-mediated injury in immune complex disease is linked to local activation of renin-angiotensin system: the role of NF-AT pathway

FcR provides a critical link between ligands and effector cells in immune complex diseases. Emerging evidence reveals that angiotensin (Ang)II exerts a wide variety of cellular effects and contributes to the pathogenesis of inflammatory diseases. In anti-glomerular basement membrane Ab-induced glomerulonephritis (GN), we have previously noted that FcR-deficient mice (gamma(-/-)) surviving from lethal initial damage still developed mesangial proliferative GN, which was drastically prevented by an AngII type 1 receptor (AT1) blocker. We further examined the mechanisms by which renin-Ang system (RAS) participates in this immune disease. Using bone marrow chimeras between gamma(-/-) and AT1(-/-) mice, we found that glomerular injury in gamma(-/-) mice was associated with CD4(+) T cell infiltration depending on renal AT1-stimulation. Based on findings in cutaneous delayed-type hypersensitivity, we showed that AngII-activated renal resident cells are responsible for the recruitment of effector T cells. We next examined the chemotactic activity of AngII-stimulated mesangial cells, as potential mechanisms coupling RAS and cellular immunity. Chemotactic activity for T cells and Th1-associated chemokine (IFN-gamma-inducible protein-10 and macrophage-inflammatory protein 1alpha) expression was markedly reduced in mesangial cells from AT1(-/-) mice. Moreover, this activity was mainly through calcineurin-dependent NF-AT. Although IFN-gamma-inducible protein-10 was NF-kappaB-dependent, macrophage-inflammatory protein 1alpha was dominantly regulated by NF-AT. Furthermore, AT1-dependent NF-AT activation was observed in injured glomeruli by Southwestern histochemistry. In conclusion, our data indicate that local RAS activation, partly via the local NF-AT pathway, enhances the susceptibility to T cell-mediated injury in anti-glomerular basement membrane Ab-induced GN. This novel mechanism affords a rationale for the use of drugs interfering with RAS in immune renal diseases.

Macrophages and nitric oxide as the possible cellular and molecular basis for strain and gender differences in susceptibility to autoimmune central nervous system inflammation

PVG rats are resistant to actively induced experimental autoimmune encephalomyelitis (EAE) and this appears to be directly related to high and sustained systemic levels of reactive nitrogen intermediates(RNI) following sensitization for EAE when compared to the highly susceptible Lewis rat. An apparent cellular basis for the different EAE susceptibility between the two rat strains is described. Spleens of PVG rats have increased monocyte/macrophage numbers(NO producing cells) and lower erythrocyte (NO scavengers) to nucleated spleen cell ratios compared with Lewis rats. Splenectomy demonstrated the pivotal role of the spleen in resistance to EAE as splenectomized PVG rats were rendered completely susceptible to disease induction. It was further demonstrated that EAE resistance in PVG rats is limited only to females and that only female PVG rats have increased splenic macrophage and an enhanced NO production following immunization. The males are fully susceptible to EAE and their spleen cell populations are similar to those of Lewis rats of either gender. Despite being resistant to active disease induction, immunized female PVG rats can generate EAE effector cells that are capable of passively transferring disease.Furthermore, female PVG rats are fully susceptible to passively transferred EAE. Thus, there appears to be no defect in the female PVG target tissue or in the processing or presentation of antigen,but a block at the level of effector cell expansion and/or recirculation and transmigration into the target tissue in actively induced EAE.

Mac-1(+) myelopoiesis induced by CFA: a clue to the paradoxical effects of IFN-gamma in autoimmune disease models

The mechanisms accounting for the protective role of endogenous interferon gamma (IFN-gamma) in certain murine autoimmune disease models, versus a disease-promoting role in others, have remained elusive. The protective effect of IFN-gamma might be unique to models that rely on the use of complete Freund's adjuvant (CFA) and whose pathogenesis is predominantly driven by delayed-type hypersensitivity. In these models, IFN-gamma counteracts disease development by inhibiting CFA-induced proliferation of a pathogenically important Mac-1(+) cell population(s). This calls into question our usual conceptualization of the balance between innate and specific immunity in these models, as well as their clinical relevance, particularly when the role of IFN-gamma or related cytokines is considered.

Adjuvant immunotherapy is dependent on inducible nitric oxide synthase

Rodents immunized with complete Freund's adjuvant (CFA) are resistant to subsequent attempts to induce autoimmune disease, while animals immunized with incomplete Freund's adjuvant (IFA) remain susceptible. Mycobacterial extracts can stimulate inducible nitric oxide synthase (NOS2) gene transcription. Robust expression of NOS2 has been linked to suppression of T cell proliferation and alterations in immune responses. Our studies investigated the hypothesis that the immunoprotective effect of CFA before immunization requires functional NOS2. NOS2 gene expression is chronically elevated in lymph nodes and spleens of CFA-immunized mice. Maximal expression of NOS2 after CFA immunization requires the presence of functional type I tumor necrosis factor alpha receptor (TNFR1) and interferon gamma. Groups of nontreated and CFA-preimmunized male C57BL/6J or C57BL/6NOS2(-/)- mice were immunized with myelin oligodendrocyte glycoprotein (MOG) peptide 35-55 in CFA to induce experimental allergic encephalomyelitis (EAE). Wild-type C57BL/6J mice were protected from the development of symptoms of EAE, while the NOS2(-/)- mice failed to be protected. NOS2-dependent effects of CFA included an augmentation of the MOG-specific IgG1 response, a decrease in interleukin 6 production by MOG-reactive lymphocytes, and a marked decrease in mononuclear cell infiltrates in the central nervous system. These studies support the hypothesis that CFA immunization modulates immune responses through a nitric oxide-dependent mechanism.

Antigen processing of vesicular stomatitis virus in situ. Interdigitating dendritic cells present viral antigens independent of marginal dendritic cells but fail to prime CD4(+) and CD8(+) T cells

Acute macrophage (M phi) depletion, using a liposome-mediated 'suicide technique', markedly suppressed priming of splenic CD4(+) and CD8(+) T-cell responses to vesicular stomatitis virus (VSV). However, phagocytic marginal dendritic cells (MDC), but not interdigitating dendritic cells (IDC), are now known to be also depleted by this technique. To clarify the role splenic dendritic cell (DC) subsets and M phi play in priming for a virus-specific T-cell-mediated immune response, DC and M phi were purified from VSV-infected mice and assayed for the presence of epitopes recognized by VSV helper T (Th) cells and cytotoxic T lymphocytes (CTL). Antigen pulse experiments performed in situ demonstrated that VSV Th cell and CTL epitopes became transiently associated only with DC, but not M phi or B cells, indicating that DC represent the critical antigen-presenting cell (APC) population in vivo for this virus. The failure of MDC/M phi-deficient mice to become primed was not due to the complete elimination of antigen-presenting DC because VSV peptide/class I and II complexes were detected on IDC following lipsome-mediated elimination of phagocytic cells. However, the VSV-induced chemokine response was dramatically suppressed in these mice. Thus, despite the expression of VSV peptide/class I and II complexes, IDC are not sufficient to prime VSV Th cells in the absence of MDC and/or splenic M phi.

T- and B-cell nonresponsiveness to self-alphaB-crystallin in SJL mice prevents the induction of experimental allergic encephalomyelitis

The myelin-associated stress protein alphaB-crystallin triggers strong proliferative responses and IFN-gamma production by human T cells and it is considered a candidate autoantigen in multiple sclerosis. In this study we examined the capacity of alphaB-crystallin or peptides derived thereof to induce experimental autoimmune encephalomyelitis (EAE) in SJL mice. Despite extensive efforts to induce EAE using active immunization with whole alphaB-crystallin, using adoptive transfer of lymphocytes or using peptide immunizations, no clinical or histological signs of EAE could be induced. SJL mice were unable to mount proliferative T-cell responses in vitro or delayed-type hypersensitivity responses in vivo to self-alphaB-crystallin. Also, immunization with self-alphaB-crystallin did not lead to any antibody response in SJL mice while bovine alphaB-crystallin triggered clear antibody responses within 1 week. Immunizations with alphaB-crystallin-derived peptides led to the activation of IL-4-producing Th2 cells and only a few IFN-gamma-producing Th1 cells. Peptide-specific T cells showed no cross-reactivity against whole alphaB-crystallin. The inability of SJL mice to mount proinflammatory T-cell responses against self-alphaB-crystallin readily explains the lack of EAE induction by immunization with whole protein or peptides derived from it. T- and B-cell nonresponsiveness is associated with constitutive expression of full-length alphaB-crystallin in both primary and secondary lymphoid organs in SJL mice, which is seen in other mammals as well, but not in humans.

Identification of genetic loci controlling the characteristics and severity of brain and spinal cord lesions in experimental allergic encephalomyelitis

Experimental allergic encephalomyelitis (EAE) is the principal genetically determined animal model for multiple sclerosis (MS), the major inflammatory disease of the central nervous system (CNS). Although genetics clearly play a role in susceptibility to MS, attempts to identify the underlying genes have been disappointing. Considerable variation exists between MS patients with regard to the severity of clinical signs, mechanism of demyelination, and location of CNS lesions, confounding the interpretation of genetic data. A mouse-human synteny mapping approach may allow the identification of candidate susceptibility loci for MS based on the location of EAE susceptibility loci. To date, 16 regions of the mouse genome have been identified that control susceptibility or clinical signs of EAE. In this work, we examined the genetic control of histopathological lesions of EAE in an F2 intercross population generated from the EAE susceptible SJL/J and EAE resistant B10.S/DvTe mouse strains. Composite interval mapping was used to identify 10 quantitative trait loci (QTL), including seven newly identified loci controlling the distribution and severity of CNS lesions associated with murine EAE. QTL on chromosome 10 control lesions in the brain, whereas QTL on chromosomes 3, 7, and 12 control lesions in the spinal cord. Furthermore, sexually dimorphic QTL on chromosomes 2, 9, and 11 control CNS lesions in females, whereas QTL on chromosomes 10, 11, 12, 16, and 19 control lesions in males. Our results suggest that the severity and location of CNS lesions in EAE are genetically controlled, and that the genetic component controlling the character and severity of the lesions can be influenced by sex.

Gender-dependent IL-12 secretion by APC is regulated by IL-10

Female SJL mice preferentially mount Th1-immune responses and are susceptible to the active induction of experimental allergic encephalomyelitis. By contrast, young adult male SJL are resistant to experimental allergic encephalomyelitis due to an APC-dependent induction of Th2 cells. The basis for this gender-dependent differential T cell induction was examined by analysis of macrophage APC cytokine secretion during T cell activation. APC derived from females secrete IL-12, but not IL-10, during T cell activation. By contrast, APC derived from males secrete IL-10, but not IL-12, during T cell activation. Activation of T cells with APC derived from the opposite sex demonstrated that these cytokines were derived from the respective APC populations. Furthermore, inhibition of IL-10, but not TGF-beta, during T cell activation resulted in the secretion of IL-12 by male-derived APC. APC from naive male mice, in which IL-10 was reduced in vivo before isolation, also secrete IL-12, demonstrating altered APC cytokine secretion was due to an environment high in IL-10 before Ag encounter. Finally, APC derived from castrated male mice preferentially secrete IL-12 during T cell activation. These data demonstrate a link between gonadal hormones and APC activity and suggest that these hormones alter the APC, thereby influencing cytokine secretion during initial T cell activation.

Beta7 integrins contribute to demyelinating disease of the central nervous system

A role for alpha4 integrins in different forms of the multiple sclerosis-like disease experimental autoimmune encephalomyelitis (EAE) has been demonstrated, but the individual contributions of alpha4beta1, alpha4beta7, and the related alphaEbeta7 integrin have not been determined. The P7 integrins alpha4beta7 and alphaEbeta7 play a central role in chronic inflammation, mediating the trafficking, entry, and/or adhesion of lymphocytes in the inflamed pancreas and gut, and their ligands MAdCAM-1, VCAM-1 and E-cadherin are expressed on brain endothelial cells and/or on microvessels in the inflamed central nervous system. Here, we show that an antibody directed against the beta7 subunit greatly attenuates a non-remitting form of EAE, induced by adoptive transfer of myelin oligodendrocyte peptide (MOG35-55)-stimulated T cells. Combinational treatment with both anti-beta7 and alpha4 integrin subunit antibodies led to more rapid and complete remission than that obtained with anti-alpha4 antibody alone, potentially implicating a role for alphaEbeta7 in disease progression. Remission correlated with the down-regulation of the vascular addressins VCAM-1. MAdCAM-1, and ICAM-1 on cerebral blood vessels. Attenuated forms of disease were induced by adoptive transfer of either wild-type encephalitogenic T cells to beta7-deficient gene knockout mice, or of beta7-/-encephalitogenic T cells to wild-type recipients. The former finding indicates that beta7 + ve recruited cells contribute to disease progression. Thus alpha4beta1, alpha4beta7, and alphaEbeta7 integrins may all play a contributory role in the progression of chronic forms of demyelinating disease, and together with their ligands could represent potential targets for improved treatment of some forms of multiple sclerosis.

Activation of Regulatory Cells Suppresses Experimental Allergic Encephalomyelitis Via Secretion of IL-10

Suppression of CD4+ Th1 cell-mediated autoimmune disease via immune deviation is an attractive potential therapeutic approach. CD4+ Th2 T cells specific for myelin basic protein, induced by immunization of young adult male SJL mice, suppress or modify the progression of CNS autoimmune disease. This report demonstrates that activation of non-neuroantigen-specific Th2 cells is sufficient to suppress both clinical and histological experimental allergic encephalomyelitis (EAE). Th2 cells were obtained following immunization of male SJL mice with keyhole limpet hemocyanin. Transfer of these cells did not modify EAE, a model of human multiple sclerosis, in the absence of cognate Ag. Disease suppression was obtained following adoptive transfer and subcutaneous immunization. Suppression was not due to the deletion of myelin basic protein-specific T cells, but resulted from the presence of IL-10 as demonstrated by the inhibition of Th2-mediated EAE suppression via passive transfer with either anti-IL-10 or anti-IL-10R mAb. These data demonstrate that peripheral activation of a CD4+ Th2 population specific for an Ag not expressed in the CNS modifies CNS autoimmune disease via IL-10. These data suggest that either peripheral activation or direct administration of IL-10 may be of benefit in treating Th1-mediated autoimmune diseases.

Enhanced Autoimmune Arthritis in IFN-γ Receptor-Deficient Mice Is Conditioned by Mycobacteria in Freund’s Adjuvant and by Increased Expansion of Mac-1+ Myeloid Cells

Induction of experimental autoimmune diseases often relies on immunization with the organ-specific autoantigens in CFA, which contains heat-killed mycobacteria. In several of these models, including collagen-induced arthritis, endogenous IFN-γ acts as a disease-limiting factor in the pathogenesis of the disease. Here we show that in collagen-induced arthritis the protective effect of IFN-γ depends on the presence of mycobacteria in the adjuvant. Omission of mycobacteria inverts the role of endogenous IFN-γ to a disease-promoting factor. Thus, the mycobacterial component of CFA opens a pathway by which endogenous IFN-γ exerts a protective effect that supersedes its otherwise disease-promoting effect. Extramedullary hemopoiesis and expansion of the Mac-1+ cell population accompanied the accelerated and more severe disease course in the IFN-γ receptor knockout mice immunized with CFA. Treatment of such mice with Abs against the myelopoietic cytokines IL-6 or IL-12 inhibited both disease development and the expansion of the Mac-1+ population. We postulate that mycobacteria in CFA stimulate the expansion of the Mac-1+ cell population by a hemopoietic process that is restrained by endogenous IFN-γ. These results have important implications for the validity of animal models of autoimmunity to study the pathogenesis and to evaluate cytokine-based therapy of autoimmune diseases.

Decreased IL-12 Production Underlies the Decreased Ability of Male Lymph Node Cells to Induce Experimental Autoimmune Encephalomyelitis

Myelin basic protein (MBP)-specific T lymphocytes from male SJL mice were shown to be less encephalitogenic than MBP-specific T lymphocytes from females. Mechanisms underlying this gender difference in the induction phase of EAE were examined. Following immunization with MBP, draining lymph nodes contained fewer cells, and Ag-specific proliferative responses were decreased in males as compared with females. These gender differences in the proliferative response were not unique to MBP-specific responses since they were also observed after immunization with hen eggwhite lysozyme. Short-term MBP-specific T cell lines derived from females and males mapped with identical specificity, indicating no defect in the ability of male APCs to process Ag. Interestingly, IL-12 and IFN-γ production was decreased following Ag-specific stimulation of draining lymph node cells (LNC) from males as compared with females, but IL-10 and IL-4 were no different. While male-derived LNCs were less encephalitogenic than female derived LNCs, cotransfer and coculture of male LNCs with female LNCs demonstrated that male LNCs were not immunosuppressive. Administration of IL-12 to LNCs from male mice enhanced encephalitogenicity. These data indicate that deficient endogenous IL-12 production within draining LNCs of male SJL mice is central to gender differences in the induction phase of experimental autoimmune encephalomyelitis.

Genetic Analysis of Disease Subtypes and Sexual Dimorphisms in Mouse Experimental Allergic Encephalomyelitis (EAE): Relapsing/Remitting and Monophasic Remitting/Nonrelapsing EAE Are Immunogenetically Distinct

Experimental allergic encephalomyelitis (EAE) is the principal animal model of multiple sclerosis (MS), the major inflammatory disease of the central nervous system. Murine EAE is generally either an acute monophasic or relapsing disease. Because the clinical spectrum of MS is more diverse, the limited range of disease subtypes observed in EAE has raised concern regarding its relevance as a model for MS. During the generation of a large F2 mapping population between the EAE-susceptible SJL/J and EAE-resistant B10.S/DvTe inbred lines, we identified four distinct subtypes of murine EAE resembling clinical subtypes seen in MS. We observed acute progressive, chronic/nonremitting, remitting/relapsing, and monophasic remitting/nonrelapsing EAE. An additional subtype, benign EAE, was identified after histologic examination revealed that some mice had inflammatory infiltrates of the central nervous system, but did not show clinical signs of EAE. Genome exclusion mapping was performed to identify the loci controlling susceptibility to each disease subtype. We report three novel EAE-modifying loci on chromosomes 16, 7, and 13 (eae11–13, respectively). Additionally, unique loci with gender-specific effects govern susceptibility to remitting/relapsing (eae12) and monophasic remitting/nonrelapsing (eae7 and 13) EAE.

Treatment of multiple sclerosis with copolymer-1 (Copaxone): implicating mechanisms of Th1 to Th2/Th3 immune-deviation

The synthetic polypeptide copolymer-1 (Cop-1; Copaxone; Glatiramer Acetate) has been recently approved as an effective treatment in relapsing multiple sclerosis (MS). A large body of evidence demonstrates that Cop-1 induces active suppression of CNS-inflammatory disease in animal models. However, Cop-1-mediated suppressor mechanisms have not yet been elucidated in humans. A 12-month open study following clinical and immunological parameters of ten relapsing MS patients treated with Cop-1 is presented. Relapse rates and disability scores (EDSS) were evaluated prior to and after 12 months of treatment. The immunological parameters assessed prior to and at 3 months' interval during treatment included serum levels of soluble IL-2 receptor (sIL-2R) and IL-10 as well as leukocyte cytokine mRNA expression of TNF alpha, IL-4 and TGF-beta. Copaxone treatment was found to lead to a significant reduction in the mean annual relapse rate (from 1.4 prior to treatment to 0.6 during treatment) and stabilization of disability in 90% of the patients. The treatment was accompanied by an elevation of serum IL-10 levels, suppression of the pro-inflammatory cytokine TNF alpha mRNA, and an elevation of the anti-inflammatory cytokines TGF-beta and IL-4 mRNAs in PBLs. These results suggest that the beneficial clinical effects of Copaxone in MS patients may be attributed to changes in activation of T cell subsets and a shift from Th1 to Th2/Th3 cytokine profile, probably leading to Cop-1-driven mechanisms of bystander suppression.

Neutrophils secreting tumor necrosis factor alpha infiltrate the central nervous system of BALB/c mice with experimental autoimmune encephalomyelitis

Experimental autoimmune encephalomyelitis (EAE) can be induced in resistant BALB/c mice by ultrasound-formed adjuvant emulsion. In contrast to susceptible mouse strains large numbers of neutrophils secreting TNF-alpha occupied the central nervous system (CNS) of BALB/c mice with severe EAE, whereas only small numbers of macrophages and CD4+ T-cells could be detected. CNS infiltration was preceded with activation of microglial cells. Ultrasound formed adjuvant induced early IFN-gamma expression in popliteal lymph nodes of BALB/c mice, whereas conventional adjuvant induced delayed IFN-gamma production. Although the clinical outcome of EAE was similar to that seen in susceptible mice, the pathogenesis was distinct having possible implications on the different forms seen in multiple sclerosis.

MDP(Lysyl)GDP, a nontoxic muramyl dipeptide derivative, inhibits cytokine production by activated macrophages and protects mice from phorbol ester- and oxazolone-induced inflammation

High levels of pro-inflammatory cytokines and nitric oxide are proposed to orchestrate pathophysiologic mechanism(s) associated with various inflammatory dermatoses. This study examines whether a water soluble 3-O-[N-acetylmuramyl-L-lysyl-D-iso]-2-di-on-glycine [MDP(Lysyl)GDP], a nontoxic and nonpyrogenic derivative of muramyl dipeptide (MDP), can inhibit the in vitro production of inflammatory mediators by lipopolysaccharide- or interferon-gamma-activated macrophages, and whether such an inhibitory effect can translate into in vivo protection of mice from irritant and allergic contact dermatitis. Thioglycollate-elicited peritoneal macrophages cultured in medium alone or in medium supplemented with MDP(Lysyl)GDP (1-100 microg per ml) expressed neither mRNA transcripts for inducible nitric oxide synthase, interleukin-1beta, and tumor necrosis factor-alpha, nor cytokine proteins and nitric oxide activity. Incubation of the cells with either lipopolysaccharide or interferon-gamma for 6 h resulted in a significant induction of inducible nitric oxide synthase, interleukin-1beta, and tumor necrosis factor-alpha mRNA, and the accumulation of high levels of monokines and nitrites in cultures by 24 h. Co-incubation of the macrophages with lipopolysaccharide or interferon-gamma and MDP(Lysyl)GDP (1-100 microg per ml) resulted in a concentration-dependent suppression of the steady-state mRNA transcripts for inducible nitric oxide synthase, tumor necrosis factor-alpha, and interleukin-1beta, induced by lipopolysaccharide, but not by interferon-gamma. In mouse models of phorbol ester- and oxazolone-induced ear inflammation, topical application of MDP(Lysyl)GDP significantly suppressed ear swelling in a dose-dependent manner. Likewise, oral treatment with MDP(Lysyl)GDP at days -3, -2, and -1 before elicitation with oxazolone also significantly inhibited ear inflammation. Taken together, our findings suggest that MDP(Lysyl)GDP has the potential to be a therapeutic application in the treatment of inflammatory conditions in which overproduction of pro-inflammatory mediators are implicated to play a pathogenic role.