Regulatory circuits in autoimmunity: recruitment of counter-regulatory CD8+ T cells by encephalitogenic CD4+ T line cells

Immune response in peripheral axons delays disease progression in SOD1G93A mice

Background

Increasing evidence suggests that the immune system has a beneficial role in the progression of amyotrophic lateral sclerosis (ALS) although the mechanism remains unclear. Recently, we demonstrated that motor neurons (MNs) of C57SOD1^G93A mice with slow disease progression activate molecules classically involved in the cross-talk with the immune system. This happens a lot less in 129SvSOD1^G93A mice which, while expressing the same amount of transgene, had faster disease progression and earlier axonal damage. The present study investigated whether and how the immune response is involved in the preservation of motor axons in the mouse model of familial ALS with a more benign disease course.

Methods

First, the extent of axonal damage, Schwann cell proliferation, and neuromuscular junction (NMJ) denervation were compared between the two ALS mouse models at the disease onset. Then, we compared the expression levels of different immune molecules, the morphology of myelin sheaths, and the presence of blood-derived immune cell infiltrates in the sciatic nerve of the two SOD1G93A mouse strains using immunohistochemical, immunoblot, quantitative reverse transcription PCR, and rotating-polarization Coherent Anti-Stokes Raman Scattering techniques.

Results

Muscle denervation, axonal dysregulation, and myelin disruption together with reduced Schwann cell proliferation are prominent in 129SvSOD1^G93A compared to C57SOD1^G93A mice at the disease onset, and this correlates with a faster disease progression in the first strain. On the contrary, a striking increase of immune molecules such as CCL2, MHCI, and C3 was seen in sciatic nerves of slow progressor C57SOD1^G93A mice and this was accompanied by heavy infiltration of CD8⁺ T lymphocytes and macrophages. These phenomena were not detectable in the peripheral nervous system of fast-progressing mice.

Conclusions

These data show for the first time that damaged MNs in SOD1-related ALS actively recruit immune cells in the peripheral nervous system to delay muscle denervation and prolong the lifespan. On the contrary, the lack of this response has a negative impact on the disease course.

Electronic supplementary material

The online version of this article (doi:10.1186/s12974-016-0732-2) contains supplementary material, which is available to authorized users.

Adhesion molecules involved in neutrophil recruitment during sepsis-induced acute kidney injury

Acute kidney injury (AKI) is a common complication in critically ill patients and is associated with high mortality. Recruitment of neutrophils is a hallmark in the pathogenesis of AKI. Although ischemia-reperfusion injury (IRI) is a frequently used research model of AKI, the clinical relevance of IRI-induced AKI is limited. Epidemiologically, sepsis is the prevailing cause of kidney injury. However, it is still unknown whether these distinct entities of AKI share the same pathophysiological mechanisms. This study was initiated to investigate the molecular mechanisms of neutrophil recruitment into the kidney in a murine model of sepsis-induced AKI. By using a flow cytometry-based method, we show that the two β2-integrins Mac-1 and LFA-1 as well as E-selectin and P-selectin are involved in neutrophil recruitment into the kidney after induction of sepsis. The molecular mechanisms of neutrophil recruitment were further investigated using intravital microscopy, demonstrating that blocking one of these four molecules reduces the number of adherent leukocytes. This was accompanied by a renal upregulation of E-selectin, P-selectin and ICAM-1 (the counter-receptor of β2-integrins on endothelial cells) after sepsis induction. We conclude that blocking P-selectin, E-selectin, Mac-1 or LFA-1 protects mice from sepsis-induced AKI.

Involvement of IFN-γ and perforin, but not Fas/FasL interactions in regulatory T cell-mediated suppression of experimental autoimmune encephalomyelitis

Autoaggressive, myelin-reactive T cells are involved in multiple sclerosis and its prototype experimental autoimmune encephalomyelitis (EAE) in mice. A peripheral negative feedback mechanism involving regulatory CD4+ and CD8+T cells (Treg) operates to suppress disease-mediating T cell responses. We have recently characterized a novel population of Qa-1a-restricted, TCR-peptide-reactive CD8αα+TCRαβ+ Treg that induce apoptotic depletion of the encephalitogenic Vβ8.2 cells in vivo and provide protection from EAE. Here we have used mice deficient in perforin, Fas/FasL and IFN-γ molecules to investigate their role in Treg-mediated regulation of EAE. Data show that Fas/FasL interactions are not involved, but regulation mediated by Treg is dependent on the presence of IFN-γ and the perforin pathway. These data provide a molecular mechanism of Treg-mediated killing of the pathogenic T cells and have important implications in the design of immune interventions for demyelinating disease.

CNS infiltration of peripheral immune cells: D-Day for neurodegenerative disease?

While the central nervous system (CNS) was once thought to be excluded from surveillance by immune cells, a concept known as “immune privilege,” it is now clear that immune responses do occur in the CNS—giving rise to the field of neuroimmunology. These CNS immune responses can be driven by endogenous (glial) and/or exogenous (peripheral leukocyte) sources and can serve either productive or pathological roles. Recent evidence from mouse models supports the notion that infiltration of peripheral monocytes/macrophages limits progression of Alzheimer's disease pathology and militates against West Nile virus encephalitis. In addition, infiltrating T lymphocytes may help spare neuronal loss in models of amyotrophic lateral sclerosis. On the other hand, CNS leukocyte penetration drives experimental autoimmune encephalomyelitis (a mouse model for the human demyelinating disease multiple sclerosis) and may also be pathological in both Parkinson's disease and human immunodeficiency virus encephalitis. A critical understanding of the cellular and molecular mechanisms responsible for trafficking of immune cells from the periphery into the diseased CNS will be key to target these cells for therapeutic intervention in neurodegenerative diseases, thereby allowing neuroregenerative processes to ensue.

Antigen-Specific Therapies in Multiple Sclerosis

During recent years, many new therapies for human autoimmune diseases such as multiple sclerosis (MS) have been considered based on promising in vitro data or animal experiments. A number of them have proceeded to early clinical testing. However, very few finally advanced to approval by the regulatory agencies and are currently available to patients. The main reasons for failure were either lack of efficacy in humans and/or unexpected and untolerable adverse events. Although previous attempts toward antigen-specific immunomodulation have often been disappointing, these difficulties have led to renewed interest in therapies that aim at reestablishing tolerance to autoantigens at the level of either T cell-mediated or antibody-mediated immune responses or both. Such antigen-specific immunotherapies offer the prospect of correcting pathological immune reactivity against autoantigens in a highly specific and effective manner and also achievement of this goal with relatively little side effects. Here we will review the various approaches that are currently being considered for antigen-specific immunotherapies in MS.

Suppressor role of rat CD8+CD45RClow T cells in experimental autoimmune uveitis (EAU)

To determine whether decreased regulatory T cell activity contributes to the pathogenesis of recurrent experimental autoimmune uveitis (EAU), we compared the immunoregulatory activity of CD8+CD45RClow T cells isolated from rats that had recovered from acute EAU with those from rats with the progressive, recurrent disease. Our results showed that CD8+CD45RClow T cells isolated from the recovered rats showed suppressive activity in vitro, whereas those from rats with progressive, recurrent EAU do not. Depletion of CD8+CD45RClow T cells from T cells used for adoptive transfer of EAU increased the pathogenic activity of the T cells. Co-transfer of CD8+CD45RClow T cells with uveitogenic T cells prevented the relapse of disease in the recipient rats. The suppressive CD8+CD45RClow T cells expressed increased levels of Foxp3 after stimulation in vitro with the autoantigen, and inhibited the production of IFN-gamma by autoreactive T cells. Our data indicate that the decreased suppressive activity of CD8+CD45RClow T cells is correlated with disease development in this autoimmune disease. Further studies on the biology of this T cell population should provide much needed insights into disease pathogenesis.

Regulation of experimental autoimmune encephalomyelitis by CD4+, CD25+ and CD8+ T cells: analysis using depleting antibodies

Experimental Autoimmune Encephalomyelitis (EAE) can be induced in mice of the C57BL/6 strain by subcutaneous immunization with myelin/oligodendrocyte glycoprotein (MOG) peptide p35-55 in CFA, administered twice at an interval of one week and supplemented with Bordetella pertussis toxin given IV. Here, we studied the effect on the induction of EAE of depleting antibodies to CD4, CD8, or CD25 administered before either the first or the second dose of MOG p35-55. We found that anti-CD4 abolished EAE when given before the first immunization; anti-CD4 did not affect the disease when it was given before the second immunization. Anti-CD8 enhanced EAE induction when given before either of the two immunizations. Anti-CD25 enhanced EAE to the same degree as anti-CD8 when given before the first immunization, but anti-CD25 was even more effective in enhancing EAE when given before the second immunization. The anti-CD25 treatment led to significantly enhanced IFNgamma production by T cells responding to MOG p35-55 and persisting anti-MOG antibodies detectable 56 days after the first immunization. Administration of anti-CD8 or anti-CD25 abolished the need for pertussis toxin to induce EAE. These findings are compatible with the idea that CD4 T cells are required for the initial induction of EAE and that the disease is down-regulated by T cells expressing CD8 or CD25. These regulatory T cells exist prior to MOG immunization, but the CD25+ regulators appear to be further amplified by immunization.

Variceal bleeding: pharmacological therapy

The complications of portal hypertension are totally prevented if hepatic venous pressure gradient is decreased below 12 mm Hg. Besides, if this target is not achieved, a 20% decrease in portal pressure from baseline levels offers an almost total protection from variceal bleeding. This sets the rationale for drug therapy to reduce portal pressure in portal hypertension. Pharmacological therapy to decrease portal pressure includes vasoconstrictors to decrease portal blood inflow, vasodilators to decrease hepatic resistance, and combination therapy. Oral agents, such as beta-adrenergic blockers and organic nitrates, are used for long-term prevention of variceal bleeding, while parenteral agents, such as somatostatin (and analogues) and terlipressin, are used for the treatment of acute variceal bleeding.

Autoimmune concepts of multiple sclerosis as a basis for selective immunotherapy: from pipe dreams to (therapeutic) pipelines

Autoimmune T and B cell responses to CNS antigen(s) are thought to drive the pathogenesis of multiple sclerosis (MS), and thus are logical targets for therapy. Indeed, several immunomodulatory agents, including IFN-beta 1b, IFN-beta 1a, glatiramer acetate, and mitoxantrone, have had beneficial clinical effects in different forms of MS. However, because the available treatments are only partially effective, MS therapy needs to be further improved. Selective (antigen-specific) immunotherapies are especially appealing because in theory they combine maximal efficacy with minimal side effects. Indeed, several innovative immunotherapies have been successfully applied in experimental autoimmune encephalomyelitis. For example, autoreactive T cells can be selectively targeted by means of antigen, T cell receptor, or activation markers. However, experimental autoimmune encephalomyelitis is far from being a perfect approximation of MS because MS is more heterogeneous and the target antigen(s) is (are) not known. Further advances in MS therapy will depend on our growing understanding of the pathogenesis of this still incurable disease.

Experimental autoimmune encephalomyelitis: cytokines, effector T cells, and antigen-presenting cells in a prototypical Th1-mediated autoimmune disease

Experimental autoimmune encephalomyelitis (EAE) is widely depicted as the prototypical CD4+ Th1-mediated autoimmune disease. Microglia and perivascular macrophages are believed to act as antigen-presenting cells during the effector phase of EAE. In this article, recent data that challenge these conceptions are reviewed. Several recent studies have shown that myelin-reactive CD8+ T cells can mediate inflammatory demyelination. Furthermore, dendritic-like cells have been detected in EAE lesions and implicated in encephalitogenic T-cell activation. Although Th1 polarizing monokines, such as interleukin-12 (IL-12) and possibly IL-23, are critical for the manifestation of EAE, individual Th1 effector cytokines were found to be dispensible.

Generalization of single immunological experiences by idiotypically mediated clonal connections

Clonal interactions of B cells by idiotope-specific mutual recognition of their antigen receptors with the participation of T cells were assumed to form a web of unknown density, referred to as the idiotypic network. Although these clonal connections were proposed to fulfill important internal regulatory functions, their biological significance, especially in relation to antigen-induced immune responses, remained a mystery. In view of this, we postulate that the basic function of the idiotypic internal connection between B and T cell antigen receptors is to transform antigen-induced cellular activations, by idiotypic crossreactivity, into the regulation of cell clones with different antigen specificities. This process leads not only to the suppression of major clones but also to the activation of minor ones. The latter activating property may allow the generalization of single antigenic experiences, so that the immune system in its entirety benefits in its battle against environmental microbes. Such idiotypic clonal interactions are particularly effective in early ontogeny. During a short neonatal imprinting period, maternal immunological knowledge in the form of somatically mutated, high-affinity IgG antibodies, acquired through a continuous encounter with external antigens, guides the initial ontogenetic development of the immune system and so exerts long-lasting transgenerational advantageous effects in the offspring.

CTLA-4 gene expression is influenced by promoter and exon 1 polymorphisms

CTLA-4, expressed mainly on activated T cells, helps maintain, through its inhibitory function, immune-system homeostasis. Polymorphisms in the CTLA-4 gene (CTLA4) are known to be important in several autoimmune diseases, including multiple sclerosis (MS). Here, we have performed genotyping for CTLA4 polymorphisms, and investigated expression by peripheral blood mononuclear cells of CTLA-4 mRNA and protein, in patients with MS and myasthenia gravis and in healthy controls. Expression levels for mRNA and protein were similar in the patient and control groups; however, there was a clear relationship between genotype and CTLA-4 expression. Specifically, individuals carrying thymine at position -318 of the CTLA4 promoter (T(-318)) and homozygous for adenine at position 49 in exon 1 showed significantly increased expression both of cell-surface CTLA-4 after cellular stimulation and of CTLA-4 mRNA in non-stimulated cells. The association was seen most clearly for unsorted CD3(+) cells and was absent in the CD8(+) subset. The T(-318) allele has been shown to be negatively associated with susceptibility to MS in an earlier study by our group. Thus, we propose that the susceptibility-influencing role of CTLA4 in MS may be related to genotypically conditioned promoter function, whereby high gene expression may decrease the risk of disease.

Candidate autoantigens in multiple sclerosis

Multiple sclerosis is an inflammatory demyelinating CNS disease of putatively autoimmune origin. Novel models of experimental autoimmune encephalomyelitis (EAE) have demonstrated that T cells specific for various myelin and even nonmyelin proteins are potentially encephalitogenic. The encephalitogenic T cell response directed against different CNS antigens not only determines the lesional topography of CNS inflammation but also the composition of the inflammatory infiltrates. The heterogeneity of the lesional distribution seen in EAE might therefore be useful for the understanding of the various clinical subtypes seen in MS. In this review the possible candidate autoantigens in MS are discussed with special regard to the human T cell and B cell responses against various myelin and nonmyelin proteins.

Regulatory T cells in experimental allergic encephalomyelitis. III. Comparison of disease resistance in Lewis and Fischer 344 rats

Rats of the Fischer 344 (F344) strain are resistant to experimental allergic encephalomyelitis (EAE) induced by active immunization with guinea pig myelin basic protein (MBP) in complete Freund's adjuvant whereas Lewis (LEW) rats are susceptible even though both strains share the same I-A-like class II alleles of the MHC RT1.B locus. To determine factors that might contribute to this difference in disease susceptibility, we have compared in these two strains (1) the frequency of MBP-reactive T cells in the lymph nodes and spleens of MBP-immunized animals, (2) the dominant MBP epitopes recognized by responding T cells, (3) the ability of MBP-reactive T cells to enter the central nervous system (CNS), and (4) the frequency of CD8+ regulatory T cells (RTC) whose activity is functionally antagonistic to MBP-reactive T cells. The results indicate that MBP-reactive T cell numbers are similar in MBP-immunized F344 and LEW rats, they both recognize p68-88 as the dominant encephalitogenic epitope of MBP, and MBP-reactive T cells isolated from immunized rats and adoptively transferred to naive animals are similarly effective in penetrating the blood-brain barrier and entering the CNS, leading to pathogenesis in EAE. However, the frequency of RTC that functionally inhibit MBP-reactive T cells is greater in F344 rats.

The role of regulatory T cells in Lewis rats resistant to EAE

Adult Lewis (LEW) rats are highly susceptible to experimental autoimmune encephalomyelitis (EAE), induced actively by immunization with guinea pig (GP) myelin basic protein (MBP) in complete Freund's adjuvant or adoptively transferred with activated T lymphocytes reactive to GP MBP peptide 68-88. Once LEW rats recover from active EAE or when given MBP in incomplete Freund's adjuvant (IFA), they become resistant to further attempts to induce active or passive EAE. In this study, we examined whether such EAE-resistant rats after MBP-IFA immunization have reduced frequencies of MBP-reactive T cells, whether these T cells are anergized, and whether the activity of regulatory T cells is increased to the event that they prevent activation of MBP-specific T cell subpopulations. By limiting dilution analyses (LDA) of unfractionated splenic T cells, the levels of MBP-reactive T cells in EAE-resistant rats appeared to be approximately 5% of the levels in EAE-susceptible rats. However, a subsequent analysis of CD4+ enriched T cell populations, depleted of the CD8 subset, showed similar frequencies of MBP-reactive cells in susceptible and resistant LEW rats. Not only were the frequencies on LDA altered by suppressor cells, but also LDA comparisons based on cell proliferation and cytokine production as indicators of MBP reactive cell frequencies gave markedly different results. We conclude that MBP-reactive T cells in this model of EAE-resistant LEW rats are hyporeactive to MBP as the result of an increased activity of a regulatory subset of CD8+ T cells. These results also demonstrate that the quantitation of MBP-reactive CD4+ T cells by LDA is strongly influenced by the presence of functionally antagonistic CD8+ T cells, which cause an underestimation of responder T cell frequencies, and by the method of detecting T cell reactivity.

Regulation of experimental autoimmune encephalomyelitis by natural killer (NK) cells

In this report, we establish a regulatory role of natural killer (NK) cells in experimental autoimmune encephalomyelitis (EAE), a prototype T helper cell type 1 (Th1)-mediated disease. Active sensitization of C57BL/6 (B6) mice with the myelin oligodendrocyte glycoprotein (MOG)35-55 peptide induces a mild form of monophasic EAE. When mice were deprived of NK cells by antibody treatment before immunization, they developed a more serious form of EAE associated with relapse. Aggravation of EAE by NK cell deletion was also seen in beta 2-microglobulin-/- (beta 2m-/-) mice, indicating that NK cells can play a regulatory role in a manner independent of CD8+ T cells or NK1.1+ T cells (NK-T cells). The disease enhancement was associated with augmentation of T cell proliferation and production of Th1 cytokines in response to MOG35-55. EAE passively induced by the MOG35-55-specific T cell line was also enhanced by NK cell deletion in B6, beta 2m-/-, and recombination activation gene 2 (RAG-2)-/- mice, indicating that the regulation by NK cells can be independent of T, B, or NK-T cells. We further showed that NK cells inhibit T cell proliferation triggered by antigen or cytokine stimulation. Taken together, we conclude that NK cells are an important regulator for EAE in both induction and effector phases.

Induction of experimental autoimmune encephalomyelitis by CD4+ T cells specific for an astrocyte protein, S100 beta

S100 beta protein is a calcium binding protein that is not only expressed by astrocytes in the CNS, but also in many other tissues including the eye, thymus, spleen and lymph nodes. Despite this tissue distribution, which was expected to induce a firm state of self-tolerance to S100 beta, the Lewis rat mounts a strong T cell response to this autoantigen. The pathogenicity of this T cell response was demonstrated by the adoptive transfer of S100 beta-specific T cells which induced an inflammatory response in the CNS and eye of naive syngeneic recipients. The distribution of lesions in this novel model of EAE resembles that seen in some patients with MS, suggesting that the initial autoimmune insult in MS may be directed against a non-myelin antigen co-expressed in the CNS and extra-neural tissues.

Orally induced, peptide-specific gamma/delta TCR+ cells suppress experimental autoimmune uveitis

We investigated the role of gamma/delta TCR+ T cells in induction and suppression of the T cell-mediated disease experimental autoimmune uveitis. Disease induction was studied in Lewis rats perinatally depleted of alpha/beta or gamma/delta TCR+ subpopulations. Depletion of alpha/beta TCR+ cells completely abrogated disease, whereas treatment with anti-gamma/delta antibodies had no influence on onset or intensity of uveitis. However, adoptively transferred gamma/delta+ cells from orally tolerized rats could mediate suppression of uveitis in an antigen-specific fashion. Uveitis induced by a peptide derived from the uveitogenic retinal soluble antigen (S-Ag) was suppressed by gamma/delta+ cells from rats orally tolerized with the same peptide as well as HLA peptide B27PD. This disease ameliorating effect could also be observed when rats were fed with the HLA peptide before immunization with S-Ag peptide. Transfer of alpha/beta+ T cells from the same donors as well as gamma/delta+ or alpha/beta+ cells from animals fed with control peptide had no ameliorating effect.

Virus encoding an encephalitogenic peptide protects mice from experimental allergic encephalomyelitis

The association of viral infections with autoimmune central nervous system (CNS) diseases such as post-infectious encephalomyelitis and possibly multiple sclerosis (MS) prompted the investigation to understand how virus infection could modulate autoimmune responses. Recombinant vaccinia viruses encoding an encephalitogenic portion of myelin basic protein (MBP) were evaluated in an animal model for human demyelinating disease, experimental allergic encephalomyelitis (EAE). We have determined that mice vaccinated with recombinant viruses encoding an encephalitogenic region of MBP were protected from EAE. In vivo depletion of CD8+ T cells did not abrogate this protection, suggesting lack of regulation by this cell type. These studies demonstrate that virus infection may be a means to modulated immune responsiveness to CNS disease.

Circulating natural killer cells but not cytotoxic T lymphocytes are reduced in patients with active relapsing multiple sclerosis and little clinical disability as compared to controls

Triple antibody flow cytometry was used to compare the populations of CD56+ effector cells in the peripheral circulation of 29 patients with relapsing multiple sclerosis (MS) and little disability who were exacerbation-free for over 2 months and 29 healthy control subjects. Populations were characterized by two panels of antibodies (CD8, CD16, CD56 and CD3, CD8, CD56), as well as by size or granularity. In the MS patients, mature natural killer (NK) cells (CD3-CD8-CD56+) of small size and low granularity were significantly reduced compared to normals (P(0.0003). The quantities of other effector cells (cytotoxic T lymphocytes, large granular lymphocytes and monocytes) were not different in MS patients compared to the control subjects. Also, we identified a previously unrecognized population of CD56+ monocytes (CD3-CD14+CD56+) in both the normal control subjects and the MS patients which would have been misclassified as NK cells using one or two antibody cytometry employed in previous studies.

Heterogeneity of rat encephalitogenic T cells elicited by variants of the myelin basic protein (68-86) peptide

By immunizing Lewis rats with myelin basic protein (MBP) peptide variants derived from the major encephalitogenic epitope of guinea pig (MBP(68-88) and then isolating encephalitogenic T cells from these animals, we demonstrated that the variant peptides do not elicit the same encephalitogenic T cell subsets as those induced by the wild-type peptide or by intact MBP. Rather, the pathogenic T cells differed in clonal composition as reflected by their heterogeneous responses to a panel of variant peptides and by their T cell receptor usage. Thus, molecules mimicking the MBP(68-88) autoantigen can elicit pathogenic T cell subsets without necessarily cross-reacting with T cells specific for the original autoantigen. This suggests that a more clonally diverse group of pathogenic T cells might be involved in EAE than has been apparent from studies with intact MBP or its unaltered peptides.

Tolerogenic forms of auto-antigens and cytokines in the induction of resistance to experimental allergic encephalomyelitis

Resistance to experimental allergic encephalomyelitis (EAE) induction by homogenized myelin (MSCH) in complete Freund's adjuvant (CFA) and pertussigen (P) in SJL mice was seen 1 week after intravenous injection of PLP 139-151 coupled to spleen cells (PLP-ECDI-SP). Although this resistance could be transferred by spleen cells enriched for CD8+ T cells and thus had a component of immunoregulatory T cells, it was primarily due to anergy, as it was reversible by four daily injections of interleukin (II)-2 starting 3 days after the PLP-ECDI-SP. Earlier treatment with IL-2 did not reverse the tolerance. In view of the known higher sensitivity to anergy induction of Th1 than of Th2 cells, a change in the cytokine balance in the response to MSCH+CFA after anergy induction might be responsible for the resistance to EAE induction. The effect of treatment with cytokines alone on induction of EAE was therefore also determined. Short-term (1-2 weeks) daily pretreatment with IL-2 (4000 U) or TGF-beta 2 (1 micrograms) somewhat decreased the susceptibility to subsequent EAE induction, but IL-4 (5 ng), IL-10 (5 micrograms) or IL-12 (50-200 ng) had no effect under those conditions, even if low doses of PLP were injected simultaneously. Daily injections of IL-4 over an 8-week period prior to immunization, however, significantly lowered the incidence of EAE. Simultaneous injections of IFN-gamma (2000 U/day) completely abolished this effect of IL-4. The effect of these cytokines administered immediately after the immunization with MSCH + CFA + P was also examined. As shown earlier, TGF-beta 2 (100-1000 ng/day) caused a marked protection when it was given intraperitoneally on days 5-9 after injection of MSCH + CFA. IL-4 (5 ng/day), in contrast, was very protective when administered on days 0-4 and less so when given on days 5-9 or even on days 0-12. IL-10 (1 microgram/day) was not protective under these conditions and IL-12 (50 ng/day) significantly increased the severity and mortality of EAE when given on days 0-4 after MSCH + CFA.

The clonal composition of myelin basic protein-reactive encephalitogenic T cell populations is influenced both by the structure of relevant antigens and the nature of antigen-presenting cells

Studies of experimental autoimmune encephalomyelitis (EAE) in rodents have revealed that encephalitogenic T cell lines reactive with myelin basic protein (BP) are frequently dominated by clones expressing a restricted T cell receptor repertoire. Using the rat EAE model, we have begun to examine the basis for clonal dominance within BP-reactive T cell lines. We find that variations introduced into the standard protocol of periodic antigen stimulation produce marked shifts in the representation of different clones within encephalitogenic T cell populations. For example, altering the source of antigen-presenting cells (APC), while holding antigen (BP) constant, and substituting BP from guinea pig (GPBP) for that of the rat antigen (RBP) with constant APC, both cause shifts in the composition of the dominant clones within BP-reactive T cell lines. Our results suggest that: (i) adherence to an invariant protocol of antigen challenge may lead to an underestimation of the diversity of BP-reactive encephalitogenic T cell populations; and (ii) the minor structural differences between GPBP and RBP not only cause the weak immunogenicity of RBP but also result in the alteration of different T cell subsets. These observations indicate that apparent restrictions upon the repertoire of autoimmune T cells should be interpreted with caution when such cells are elicited by immunization with foreign antigens.

High incidence of spontaneous autoimmune encephalomyelitis in immunodeficient anti-myelin basic protein T cell receptor transgenic mice

We have generated TCR transgenic mice (T/R+) specific for myelin basic protein (MBP) and crossed them to RAG-1-deficient mice to obtain mice (T/R-) that have T cells expressing the transgenic TCR but no other lymphocytes. Both T/R+ and T/R- mice carry, in the lymph nodes and spleen, large numbers of the potentially encephalitogenic CD4+ anti-MBP T cells. These cells respond to MBP in vitro but show no signs of activation in vivo. Nevertheless, approximately 14% of H-2u T/R+ and 100% of H-2u T/R- mice developed spontaneous experimental autoimmune encephalomyelitis (EAE) within 12 months. These data indicate that EAE can be mediated by CD4+ anti-MBP T cells in the absence of any other lymphocytes and that nontransgenic lymphocytes that are present in T/R+ but absent in T/R- mice have a protective effect. The data also suggest that spontaneous EAE may be triggered by an in situ activation of CD4+ anti-MBP cells in the nervous system.

Vaccination with T cell receptor peptides primes anti-receptor cytotoxic T lymphocytes (CTL) and anergizes T cells specifically recognized by these CTL

We selected three peptides from the germ-line sequence of the V beta 8.2 and J beta 2.3 gene segments of the murine T cell receptor for antigen (TCR) which contained putative Kd- and Ld-restricted epitopes. Immunization of BALB/c (H-2d) mice with the V beta 8.2(67-90) 23-mer peptide 1 as well as the 15-mer V beta 8.2(95-108)-peptide 2 efficiently primed specific CD8+ cytotoxic T lymphocyte (CTL) responses in vivo against natural TCR-V beta 8.2 epitopes. V beta 8.2+ T cells were not deleted in TCR peptide-immunized mice because the fractions of V beta 8.2+ CD4+ and V beta 8.2+ CD8+ T cells in spleen and lymph nodes were not altered. The proliferative response of V beta 8.2+ T cells to stimulation by monoclonal antibody F23.2 was selectively suppressed (by 60-80%) in peptide-immunized BALB/c mice, indicating partial anergy of this T subset. Immunization of BALB/c mice with the J beta 2.3-derived peptide 3 stimulated a CD8+ CTL response against a class I-restricted epitope within this J beta segment that was also generated during natural "endogenous" processing of this self antigen. These data confirm the predictive value of major histocompatibility complex class I allele-specific motifs. The described experiments indicate that TCR peptide-primed CD8+ CTL recognize class I-restricted, natural V beta/J beta-TCR epitopes. Such anti-TCR CTL may, thus, operate in V beta-specific immunoregulation of the T cell system suppressing their functional reactivity without deleting them.

Animal models

Different models of experimental autoimmune encephalomyelitis (EAE) have been successfully applied to investigate and manifold aspects of the autoimmune pathogenesis of multiple sclerosis. Studies using myelin-specific T-cell lines that transfer EAE to naive recipient animals established that only activated lymphocytes are able to cross the endothelial blood-brain barrier and cause autoimmune disease within the local parenchyma. All encephalitogenic T cells are CD4+ Th1-type lymphocytes that recognize autoantigenic peptides in the context of MHC class II molecules. In the case of myelin basic protein (MBP) specific EAE in the Lewis rat, the T-cell response is directed against one strongly dominant peptide epitope. The encephalitogenic T cells preferentially use one particular set of T-cell receptor genes. Although MBP is a strong encephalitogen in many species, a number of other brain protein are now known to induce EAE. These include mainly myelin components (PLP, MAG, and MOG), but also, the astroglial S-100 beta protein. Encephalitogenic T cells produce only inflammatory changes in the central nervous system, without extensive primary demyelination. Destruction of myelin and oligodendrocytes in these models requires additional effector mechanisms such as auto-antibodies binding to myelin surface antigens such as the myelin-oligodendrocyte glycoprotein.

Idiotype-specific autologous T-cell interactions restricted by HLA-DR

T lymphocytes, primed in vitro to alloantigens were shown to acquire a profound capacity to stimulate autologous T-cell proliferative responses. Both PBLs and purified peripheral T cells responded to alloreactive aTLCs, suggesting that the T/T interaction did not require processing and presentation of antigen by APCs. The T/T interactions were intrinsically MHC restricted, since the autologous T-cell response was blocked by the addition of mAbs to HLA-DR. In secondary responses, primed T-cell lines responded with a higher magnitude to the priming aTLC relative to other aTLCs with different alloantigenic specificities. This specificity of response supports a model of idiotypic TcR recognition by the responding cells. Indeed, TcR protein purified from the cell surface of the priming aTLC could stimulate the primed T-cell lines in secondary responses. Reciprocal interactions between TcRs were ruled out. These data suggest that T-cell-mediated, MHC-restricted, TcR-specific, autologous T-cell responses may be important in peripheral immune regulation.

Mercury-induced autoreactive anti-class II T cell line protects from experimental autoimmune encephalomyelitis by the bias of CD8+ antiergotypic cells in Lewis rats

Brown-Norway (BN) rats injected with HgCl2 develop a systemic autoimmune disease associated with a polyclonal B cell activation, due to autoreactive T cells specific for self-class II molecules, while Lewis (LEW) rats injected with HgCl2 do not exhibit autoimmunity and develop a non-antigen-specific, CD8-mediated immunosuppression assessed by a depression of T cell functions, and a protection against experimental autoimmune encephalomyelitis (EAE). Resistance to HgCl2-induced autoimmunity is not due to these suppressor cells since treatment with an anti-CD8 monoclonal antibody (mAb) did not allow autoimmunity to appear. The absence of autoimmunity in this strain could result from the absence of autoreactive T cells, or from quantitative or qualitative differences of these cells between susceptible and resistant strains. In the present study, we show that CD4+ anti-class II T cells are present in HgCl2-injected LEW rats and are as frequent as in BN rats when assessed by limiting dilution analysis. LEW CD4+ autoreactive T cell lines were derived. They proliferated in the presence of normal class II-bearing cells, secreted interleukin 2, and did not induce B cells to produce immunoglobulins. Transfer of one of these lines, LEW Hg A, into normal LEW rats led to the appearance of CD8+ cells responsible for a non-antigen-specific immunosuppression that induced complete protection from EAE. Immunosuppression was abrogated after treatment with an anti-CD8 mAb. In vitro, CD8+ cells from rats injected with the LEW Hg A T cell line proliferated in the presence of activated T cells whatever their origin. We conclude that HgCl2 induces CD4+ autoreactive T cells that proliferate in the presence of class II+ cells in susceptible BN as well as in resistant LEW rats. But while these cells collaborate with B cells to produce autoantibodies in BN rats, they initiate in LEW rats a suppressor circuit involving antiergotypic CD8+ suppressor cells.

Human T cell autoimmunity against myelin basic protein: CD4+ cells recognizing epitopes of the T cell receptor beta chain from a myelin basic protein-specific T cell clone

We have investigated whether the normal immune system contains T cells that are able to recognize T cell receptor (TcR) determinants of autologous autoantigen-specific T cells. The T cell clone HW.BP3, specific for myelin basic protein (MBP) was isolated from a healthy donor. HW.BP3 is restricted by HLA-DR2a, and reacts to human MBP 139-153. The expressed alpha beta TcR genes of HW.BP3 were cloned and sequenced, and the sequences analyzed for potential T cell epitopes. Two synthetic peptides, one from the VDJ beta junctional (beta 1) and one from the V beta region (beta 2) of the TcR of HW.BP3, were used to select four TcR peptide-specific T cell lines from the donor of HW.BP3. All anti-TcR lines had the phenotype CD3+/CD4+/HLA-DR+/CD25+/CD45RO+, and recognized the antigen in the context of HLA-DR. Three anti-TcR lines, which had been selected for reactivity to peptide beta 1, recognized exclusively this peptide restricted by HLA-DR2b. One anti-TcR line, selected for peptide beta 2, responded to both peptides beta 1 and beta 2 when presented by autologous blood mononuclear cells, but not by HLA-DR2a- or HLA-DR2b-transfected L cells. All TcR peptide-specific T cell lines were efficiently cytotoxic. They specifically lysed autologous macrophages or HW.BP3 line cells in the presence of exogenous peptide antigen. In contrast, HW.BP3 did not present endogenous TcR peptides to the anti-TcR lines. The results demonstrate that the normal human immune system contains not only autoantigen-specific T cells, but also T cells that recognize antigenic determinants of autologous autoreactive TcR.

Prevention of experimental autoimmune encephalomyelitis in Lewis rats by treatment with an anti-rat CD5 antibody (OX19)

Treatment of Lewis rats with a single dose of OX19 antibody, specific for rat CD5, uniformly prevented the development of experimental autoimmune encephalomyelitis (EAE). This protective effect had several notable characteristics: (1) it persisted for at least 10 days; (2) it could be achieved with either high doses of the antibody (> 200 micrograms) or lower doses (100-200 micrograms), which did not deplete T cell populations; and (3) the treated animals were able to mount comparable T cell responses to both myelin basic protein and myelin-unrelated antigens. In addition, antibody treatment consistently prevented the development of adoptively transferred EAE, suggesting that enhanced suppressor cell activity may have contributed to the protection. Antibodies such as OX19 appear capable of blocking the development of EAE, and perhaps other autoimmune diseases as well.

Synthetic peptides representing sequence 39 to 59 of rat V beta 8 TCR fail to elicit regulatory T cells reactive with V beta 8 TCR on rat encephalitogenic T cells

Subpathogenic doses of syngeneic autoreactive T cells protect experimental animals against associated autoimmune disease. Preferential use of the TCR of encephalitogenic T cells suggests that this molecule serves as the target for immunoregulation in experimental autoimmune encephalomyelitis (EAE). Whether peptides derived from the V beta 8 of the rat TCR elicit regulatory T cells and produce the same vaccinating effect against EAE as do whole T cells remains unknown. Here we show that immunization of Lewis rats with V beta 8(39-59), a peptide representing residues 39 to 59 of the rat V beta 8 TCR, does not induce the production of regulatory T cells reactive to the intact TCR V beta 8 containing this sequence. Moreover, animals that had recovered from both actively induced EAE and transferred EAE did not generate regulatory T cells that recognized the V beta 8(39-59) peptide. Further, transfusion of large doses of peptide-specific T cells did not protect the animals from EAE. Our results suggest that the V beta 8(39-59) peptide may comprise so-called cryptic epitopes, which function as immunogens only when dissociated from large protein complexes.

Immune regulation in self tolerance: functional elimination of a self-reactive, counterregulatory CD8+ T lymphocyte circuit by neonatal transfer of encephalitogenic CD4+ T cells lines

Transfer of encephalitogenic, CD4+ T lymphocyte lines into syngeneic adult Lewis rats not only leads to the development of experimental autoimmune encephalomyelitis (EAE), but, in addition, to the expansion of counterregulatory, CD8+ T lymphocyte clones which are able to lyse specifically the encephalitogenic T cells in vitro and to neutralize their encephalitogenic capacity in vivo. In striking contrast, in neonatal rats, which still lack myelin (autoantigens), injection of the same encephalitogenic lines neither mediates EAE, nor confers protection in later life against the myelin-specific T cells. In fact, this treatment results in the life-long functional elimination of counterregulatory, clonotypic CD8+ T lymphocytes, which cannot even be reinduced by repeated injections of the relevant CD4+ T line. These data seem to point to a self-protective T cell control mechanism which is developed within the immune system prior to, and thus independent of the appearance of the appropriate self antigen.

Control of experimental autoimmune uveoretinitis by low dose T cell vaccination

Autoimmune T lymphocytes can be used under appropriate conditions to induce resistance to the specific autoimmune disease that they usually produce. This practice, termed T cell vaccination, was found to be effective with the injection of a low (subpathogenic) number of autoaggressive T line lymphocytes. We report here that T cell vaccination produced marked resistance to the expression of experimental autoimmune uveoretinitis (EAU) in Lewis rats. In addition, vaccination led to the appearance of lymphoid cells in the vaccinated rats that demonstrated proliferative responses against idiotypic and ergotypic specificities of the injected T cells. This is the first report demonstrating the effector T lymphocytes specific for ocular antigens may be used as agents to modulate immunopathogenic responses responsible for EAU.

Characterization of rat encephalitogenic T cells bearing non-Vβ8 T cell recepotors

In this study, we demonstrate that T cell lines specific for a synthetic peptide representing sequence 87 to 99 of myelin basic protein (MBP) are encephalitogenic in Lewis rats. However, unlike syngeneic T cells specific for MBP residues 68 to 88 which exclusively use V beta 8 in their antigen receptors, these cells do not. None of the 10 T cell lines and T hybridomas specific for MBP (87-99) used V beta 8 in their T cell receptors. Our results document for the first time that rat encephalitogenic T cells do not exclusively use V beta 8 in T cell receptors that rat encephalitogenic T cells specific for MBP (87-99) are heterogeneous and that MBP (87-99) contains at least two epitopes for rat T cells.

Testicular lesions and lymphocyte subpopulations in rats immunized with a soluble fraction of testicular homogenate

A soluble fraction obtained from a testicular homogenate by precipitation with ammonium sulphate (ASPM) was emulsified with Freund's complete adjuvant (CFA) and injected into Wistar rats. At 50 days after the first immunization (total of three injections) the animals had developed moderate and multifocal testicular damage, characterized mainly by sloughing of the seminiferous epithelium. A delayed-type hypersensitivity response and circulating antibodies to ASPM were detected at different times with maximum levels at 50 days. The addition of Bordetella pertussis to the immunization did not increase the severity of the lesion but augmented the cellular and humoral immune response to ASPM. The phenotypic characterization of cells present in the lymph nodes draining from the site of immunization in animals injected with CFA alone (control group) revealed an increase in CD8+ T-cells and a low CD4/CD8 ratio. Conversely, rats immunized with CFA plus ASPM (experimental group) exhibited testicular damage and showed a significant decrease in CD8+ cells with a normal CD4/CD8 ratio. In conclusion, rats immunized with a testicular antigen developed focal aspermatogenic lesions and a concomitant specific immune response as well as lymph-node cell variations focused apparently on the CD8+ T-cell subpopulation.

CD4-CD8- splenic T cells from Lewis rats recovered from experimental autoimmune encephalomyelitis respond to encephalitogenic T cells that mediate this disorder

We previously demonstrated that encephalitogenic CD4+ T lymphocytes from the long-term cultured line S1, specific for myelin basic protein, induce a CD8+ T cell population in vivo that protects naive Lewis rats against experimental autoimmune encephalomyelitis caused by S1 cells. In order to determine the contribution of individual T cell population in the development of induced resistance, we have analyzed the in vitro proliferative capacity of phenotypically distinct T cell populations isolated from S1-immunized rats. We found that both CD8+ and CD8-CD4- T cells show striking proliferative responses when stimulated with S1 cells, whereas CD4+ T cells show only minimal responses. In addition, a significant proportion of the CD8-CD4- cells, after stimulated by S1 cells, became CD8+ and had a strong cytolytic activity toward S1 cells. These results suggest a contribution of double-negative splenic T cells in the regulatory circuit associated with autoimmune encephalomyelitis.

Experimental hypersensitivity pneumonitis: suppressor cell influences

Experimental hypersensitivity pneumonitis (EHP) can be transferred to strain 2 guinea pigs by lymph node cells (LNC) cultured in vitro with antigen. Using mixtures of cell populations, we sought to determine if functional suppressor cells were present in our system. We also characterized the composition of cell populations that were capable (blast 10 micrograms/mL Micropolyspora faeni from 2-week donor animals) and incapable (blast 0 micrograms/mL M. faeni from 2-week donor animals; blast 10 micrograms/mL from 8-week donor animals) using flow cytometry, anti-Ig and monoclonal antibody 8BE6 (T cell marker) of transferring EHP. Two groups of donors were used: animals sensitized with Freund's adjuvant and M. faeni and challenged with either two or eight weekly intratracheal (IT) injections of M. faeni (2- and 8-week groups). LNC from donor animals were cultured with a soluble extract of M. faeni (10 or 0 micrograms/mL) blasts isolated and transferred IV to syngeneic recipients. Control animals received media IV. Recipients were challenged IT with M. faeni 48 h after the cell transfer and sacrificed 4 days thereafter. All animals were maintained in HEPA filtered air. Randomly selected microscopic fields of the lung (250/animal) were judged to be normal or abnormal without knowledge of treatment. There was a low level of pulmonary response to an IT challenge of M. faeni in media recipients. There was a substantial increase (P less than .01) in pulmonary abnormalities in the animals receiving blasts from the 10-micrograms/mL M. faeni 2-week group. Addition of cells from incompetent cell populations (0 micrograms/mL M. faeni 2-week donors or 10 micrograms/mL M. faeni 8-week donors) did not alter the ability of competent populations to transfer EHP. Cells cultured with antigen had a decreased proportion of T cells and an increased proportion of SIg+ and large cells. Competent and incompetent cell populations did not differ in regard to proportion of large cells, surface Ig+, or T cells. We conclude that the inability of certain cell populations to transfer EHP is not associated with the appearance of functional suppressor cells. Differences of ability to transfer EHP do not correlate with differences of size distribution or T and B cell composition.

In vivo evidence for CD4+ and CD8+ suppressor T cells in vaccination-induced suppression of murine experimental autoimmune thyroiditis

In several experimental autoimmune diseases, including experimental autoimmune thyroiditis (EAT), vaccination with attenuated autoantigen-specific T cells has provided protection against subsequent induction of disease. However, the mechanism(s) of vaccination-induced suppression remains to be clarified. Since we have previously shown that suppression generated by pretreatment with mouse thyroglobulin (MTg) or thyroid-stimulating hormone in EAT is mediated by CD4+, not CD8+, suppressor T cells, we examined the role of T cell subsets in vaccination-induced suppression of EAT. Mice were vaccinated with irradiated, MTg-primed, and MTg-activated spleen cells and then challenged. Pretreatment with these cells suppressed EAT induced by immunization with MTg and adjuvant, but not by adoptive transfer of thyroiditogenic cells, suggesting a mechanism of afferent suppression. The activation of suppressor mechanisms did not require CD8+ cells, since mice depleted of CD8+ cells before vaccination showed reduced EAT comparable to control vaccinated mice. Furthermore, depletion of either the CD4+ or the CD8+ subset after vaccination did not significantly abrogate suppression. However, suppression was eliminated by the depletion of both CD4+ and CD8+ cells in vaccinated mice. These results provide evidence for the cooperative effects of CD4+ and CD8+ T cells in vaccination-induced suppression of EAT.

Autoimmunity in non-human primates: the role of major histocompatibility complex and T cells, and implications for therapy

Two autoimmune disease models were studied in rhesus monkeys: type II collagen-induced arthritis (CIA) and experimental allergic encephalomyelitis (EAE). Unrelated outbred animals were used in these studies. In both models disease resistant and susceptible individuals could be identified. Susceptibility correlated with in vitro cellular responsiveness to antigen in the CIA model. In both models resistant as well as susceptible individuals developed a humoral response to the inducing antigen. However, there is an indication that IgM antibodies play a crucial role in the induction of CIA. No clear association between major histocompatibility complex (MHC) type and disease incidence was found although a higher frequency of a certain DR type was observed in EAE susceptible monkeys. It is likely that both the antigen binding capacity of the MHC class II molecules and the T-cell repertoire play an important role in determining whether disease will develop or not.

Adjuvant effect of liposomes in the autoimmune response to rat male accessory glands

Wistar rats submitted to 3 intravenous (i.v.) or intraperitoneal (i.p.) immunizations with saline extract of rat male accessory glands (RAG) associated to liposomes developed a delayed type hypersensitivity (DTH) response to RAG after the first immunization, a remission state after the second immunization and a specific DTH response after the third injection. In a further study we transferred spleen mononuclear (SpM) cells from i.p. immunized rats taken 10 days after the second immunization (DTH negative) to normal or immunized recipients 24 h before or 10 days after the first immunization with RAG liposomes, respectively. The DTH response was reduced only in recipients previously immunized. Besides, it was possible to show that the transfer of SpM cells present when the response increased after the third injection in i.p. immunized donors reduced the suppression observed after the second injection. Rat accessory gland biopsies taken 10 days after the last immunization showed in nearly all cases mast cells, plasma cells and eosinophils with scarce lymphoid elements and increased acinar desquamation. This kind of infiltration had characteristics of cutaneous basophil hypersensitivity.

Lymphocyte subsets in the lymph nodes of rats with autoimmune orchitis

We determined temporal variations of cell subpopulations in the immunization draining lymph nodes during the development of an experimental autoimmune orchitis (EAO) induced in Wistar rats. A phenotypic characterization of T cells and their subsets (CD4+ and CD8+), B, and Ia+ cells was performed by immunofluorescent technique. At the end of the immunization period (30 days), rats injected with testicular homogenate plus adjuvants presented a considerable increase in absolute cell number but normal lymphocyte subset percentages. Testicular damage became evident at 50 days after the first immunization and increased its severity at 80 days: animals that developed EAO presented a lower number of CD8+ cells as compared with undamaged rats. This latter group showed a low CD4/CD8 ratio due to the high proportion of CD8+ cells, which could probably have a suppressor function. At 80 days massive testicular infiltration and decreased absolute cell number in lymph nodes suggest the possible migration of specific lymphocytes to the target organ.

Treatment of adjuvant arthritis in rats: vaccination potential of a synthetic nonapeptide from the 65 kDa heat shock protein of mycobacteria

Adjuvant arthritis induced by mycobacteria in rats is a widely used model of chronic arthritis. A previously described nonapeptide (Thr-Phe-Gly-Leu-Gln-Leu-Glu-Leu-Thr, amino acid sequence 180-188) from the recombinant 65 kDa heat shock protein of Mycobacterium bovis BCG, which was found to contain a T-cell epitope recognized by both arthritogenic and protective T-cell clones in vitro, has been investigated for its vaccination and therapeutic potential in adjuvant arthritis in rats. The nonapeptide was found not to be arthritogenic, although the T cells from nonapeptide immunized rats cross-react in vitro with mycobacterial antigens. Intraperitoneal administration of 0.1 mg nonapeptide in oil at day -20 or days -2, -1 and 0, resulted in a marked reduction of incidence and severity of adjuvant arthritis. The disease process and severity were also influenced by therapeutic treatment with 0.1 mg nonapeptide injected intraperitoneally at days 7 to 10. Interestingly, subplantar or intravenous application of the nonapeptide had no influence on the disease process. Deletion of the N-terminal threonine led to complete loss of in vivo activity of the nonapeptide.