Experimental Allergic Encephalomyelitis Susceptibility Research Articles

Histamine H2receptor signaling × environment interactions determine susceptibility to experimental allergic encephalomyelitis

Histamine and its receptors are important in both multiple sclerosis and experimental allergic encephalomyelitis (EAE). C57BL/6J (B6) mice deficient for the histamine H2 receptor (H2RKO) are less susceptible to EAE and exhibit blunted Th1 responses. However, whether decreased antigen-specific T-cell effector responses in H2RKO mice were due to a lack of H2R signaling in CD4(+) T cells or antigen-presenting cells has remained unclear. We generated transgenic mice expressing H2R specifically in T cells on the H2RKO background, and, using wild-type B6 and H2RKO mice as controls, induced EAE either in the presence or absence of the ancillary adjuvant pertussis toxin (PTX), which models the effects of infectious inflammatory stimuli on autoimmune disease. We monitored the mice for clinical signs of EAE and neuropathology, as well as effector T-cell responses using flow cytometry. EAE severity and neuropathology in H2RKO mice expressing H2R exclusively in T cells become equal to those in wild-type B6 mice only when PTX is used to elicit disease. EAE complementation was associated with frequencies of CD4(+)IFN-γ(+) and CD4(+)IL-17(+) cells that are equal to or greater than those in wild-type B6, respectively. Thus, the regulation of encephalitogenic T-cell responses and EAE susceptibility by H2R signaling in CD4(+) T cells is dependent on gene × environment interactions.

Histamine H3 Receptor Integrates Peripheral Inflammatory Signals in the Neurogenic Control of Immune Responses and Autoimmune Disease Susceptibility

Histamine H3 receptor (Hrh3/H3R) is primarily expressed by neurons in the central nervous system (CNS) where it functions as a presynaptic inhibitory autoreceptor and heteroreceptor. Previously, we identified an H3R-mediated central component in susceptibility to experimental allergic encephalomyelitis (EAE), the principal autoimmune model of multiple sclerosis (MS), related to neurogenic control of blood brain barrier permeability and peripheral T cell effector responses. Furthermore, we identified Hrh3 as a positional candidate for the EAE susceptibility locus Eae8. Here, we characterize Hrh3 polymorphisms between EAE-susceptible and resistant SJL and B10.S mice, respectively, and show that Hrh3 isoform expression in the CNS is differentially regulated by acute peripheral inflammatory stimuli in an allele-specific fashion. Next, we show that Hrh3 is not expressed in any subpopulations of the immune compartment, and that secondary lymphoid tissue is anatomically poised to be regulated by central H3R signaling. Accordingly, using transcriptome analysis, we show that, inflammatory stimuli elicit unique transcriptional profiles in the lymph nodes of H3RKO mice compared to WT mice, which is indicative of negative regulation of peripheral immune responses by central H3R signaling. These results further support a functional link between the neurogenic control of T cell responses and susceptibility to CNS autoimmune disease coincident with acute and/or chronic peripheral inflammation. Pharmacological targeting of H3R may therefore be useful in preventing the development and formation of new lesions in MS, thereby limiting disease progression.

H1R expression by CD11B+ cells is not required for susceptibility to experimental allergic encephalomyelitis

The histamine H1 receptor (Hrh1/H1R) was identified as an autoimmune disease gene in experimental allergic encephalomyelitis (EAE), the principal autoimmune model of multiple sclerosis (MS). Previously, we showed that selective re-expression of H1R by endothelial cells or T cells in H1RKO mice significantly reduced or complemented EAE severity and cytokine responses, respectively. H1R regulates innate immune cells, which in turn influences peripheral and central nervous system CD4+ T cell effector responses. Therefore, we selectively re-expressed H1R in CD11b+ cells of H1RKO mice to test the hypothesis that H1R signaling in these cells contributes to EAE susceptibility. We demonstrate that transgenic re-expression of H1R by H1RKO-CD11b+ cells neither complements EAE susceptibility nor T cell cytokine responses highlighting the cell-specific effects of Hrh1 in the pathogenesis of EAE and MS, and the need for cell-specific targeting in optimizing therapeutic interventions based on such genes.

H1R signaling in antigen presenting cells is dispensable for eliciting pathogenic T cells in experimental allergic encephalomyelitis (123.14)

Abstract The histamine H1 receptor (Hrh1/H1R) was identified as a shared autoimmune disease (SAID) gene in experimental allergic encephalomyelitis (EAE) and autoimmune orchitis, the principal AI models of multiple sclerosis (MS) and idiopathic male infertility, respectively. As a SAID gene, Hrh1/H1R can exert effects in multiple cell types including endothelial cells, T cells, and antigen presenting cells at critical check points during both the induction and effector phases of disease. In this regard, we showed that selective re-expression of H1R by endothelial cells in Hrh1-KO (H1RKO) mice significantly reduced disease severity whereas H1R expression by H1RKO T cells complemented EAE severity and cytokine responses. Given that the H1R has been reported to influence innate immune cell maturation, differentiation, chemotaxis, and cytokine production, which in turn influences CD4+ T cell effector responses, we selectively re-expressed H1R in CD11b+ myeloid cells of H1RKO mice to test the hypothesis that H1R signaling in these cells contributes to EAE susceptibility and/or T cell effector responses. We demonstrate that transgenic re-expression of H1R by H1RKO-CD11b+ cells neither complements EAE susceptibility nor T cell cytokine responses. These results further highlight the cell-specific effects that an AID gene can play in the pathogenesis of complex diseases such as EAE and MS, and the need for cell-specific targeting in optimizing therapeutic interventions based on such genes.

The role of the activating versus inhibitory classes of G protein coupled histamine receptors on experimental allergic encephalomyelitis susceptibility. (47.2)

Abstract Multiple sclerosis (MS) is a chronic inflammatory demyelinating disease of the central nervous system (CNS) augmented by histamine (HA) and histamine receptor (HR) signaling. To help elucidate the mechanism behind HA and HR signaling on MS susceptibility, we utilize the experimental allergic encephalomyelitis (EAE) mouse model for MS and implement the use of traditional gene knockout studies. HA is known to exert its effects through four different G protein coupled receptors (GPCRs) designated as H1R, H2R, H3R and H4R. H1R and H2R couples to the Gαq/11 and Gs class of activating G proteins, respectively, whereas H3R and H4R couples to the Gi/o class of inhibitory G proteins. Each individual HR has been shown to influence EAE pathogenesis. Here we assessed the overall contribution to EAE susceptibility imposed by the two classes of GPCRs by generating C57BL6/J mice deficient for both H1R and H2R (H1H2RKO), as well as mice deficient for both H3R and H4R (H3H4RKO). The results of our study show that H1H2RKO mice exhibit decreased susceptibility to EAE, less severe neuroinflammation with a higher infiltration of T regulatory cells into the CNS, and decreased blood brain barrier permeability compared to H3H4RKO mice. Moreover, we show that splenocytes from immunized H1H2RKO mice produce significantly less IFN-γ and IL-17, which are cytokines known to exacerbate disease. Therefore, the activating class of GPCRs enhances EAE susceptibility compared to the inhibitory class of HRs.

Evidence supporting the existence of a novel histaminergic pathway in the regulation of EAE susceptibility (143.51)

Abstract Histamine (HA) is a key regulator of experimental allergic encephalomyelitis (EAE), the autoimmune disease model of multiple sclerosis (MS). Histidine decarboxylase deficient mice (HDCKO), which are unable to synthesize HA, exhibit more severe EAE and increased IFN-γ production by splenocytes in response to MOG35-55. HA exerts its effects through four different G protein coupled receptors (GPCR): H1, H2, H3 and H4 (H1-4R). Each HA-receptor has been shown to influence EAE pathogenesis. In the mammalian brain there is, however, evidence for the existence of non-GPCR signaling by HA which is picrotoxin-sensitive and mediated by chloride conductance. GABAA receptor subunits can form HA-gated chloride channels in vitro suggesting that an ionotropic HA-receptor might contain known ligand-gated chloride channel subunits. To test the hypothesis that non-GPCR signaling by HA plays a role in immune responses, we generated H1-4RKO mice and studied their susceptibility to EAE. Here we report that in contrast to HDCKO mice, H1-4RKO mice develop less severe EAE compared to WT animals. Furthermore, splenocytes from immunized H1-4RKO mice produce significantly less IFN-γ compared to WT mice. Taken together these data support the existence of a novel HA signaling pathway in regulating EAE susceptibility.

A Single Nucleotide Polymorphism inTyk2Controls Susceptibility to Experimental Allergic Encephalomyelitis

Genes controlling immunopathologic diseases of differing etiopathology may also influence susceptibility to autoimmune disease. B10.D1-H2(q)/SgJ mice with a 2538 G-->A missense mutation in the tyrosine kinase-2 gene (Tyk2) are susceptible to Toxoplasma gondii yet resistant to autoimmune arthritis, unlike the wild-type B10.Q/Ai substrain. To understand whether Tyk2 is also important in a second autoimmune model, experimental allergic encephalomyelitis (EAE) was induced in B10.D1-H2(q)/SgJ (Tyk2(A)) and B10.Q/Ai (Tyk2(G)) mice with the myelin oligodendrocyte glycoprotein peptide 79-96. B10.D1-H2(q)/SgJ mice were resistant to EAE whereas B10.Q/Ai mice were susceptible, and a single copy of the Tyk2(G) allele conferred EAE susceptibility in F(1) hybrids. Furthermore, EAE resistance in B10.D1-H2(q)/SgJ mice was overridden when pertussis toxin (PTX) was used to mimic the effects of environmental factors derived from infectious agents. Numerous cytokines and chemokines were increased when PTX was included in the immunization protocol. However, only RANTES, IL-6, and IFN-gamma increased significantly with both genetic compensation and PTX treatment. These data indicate that Tyk2 is a shared autoimmune disease susceptibility gene whose genetic contribution to disease susceptibility can be modified by environmental factors. Single nucleotide polymorphisms like the one that distinguishes Tyk2 alleles are of considerable significance given the potential role of gene-by-environment interactions in autoimmune disease susceptibility.

Polymorphisms in murine histamine receptor H1 leading to differential cell surface expression influence autoimmune disease progression

Structural polymorphisms (L263P, M313V and S331P) in the third intracellular loop of the murine histamine receptor H1 (H1R) are candidates for Bphs, a shared autoimmune disease locus in experimental allergic encephalomyelitis (EAE) and experimental allergic orchitis (EAO). The P‐V‐P haplotype is associated with increased disease susceptibility (H1RS) whereas the L‐M‐S haplotype is associated with less severe disease (H1RR). Here we show that selective reexpression of the H1RS allele in T cells fully complements EAE susceptibility and production of disease associated cytokines while selective reexpression of the H1RR allele does not. Mechanistically, we show that the two H1R alleles exhibit differential cell surface expression and altered intracellular trafficking, with the H1RR allele being retained within the endoplasmic reticulum (ER). Moreover, we show that all three residues (L‐M‐S) comprising the H1RR haplotype are required for altered expression. These data are the first to demonstrate that structural polymorphisms influencing cell surface expression of a G‐protein couple receptor in T cells regulates immune functions and autoimmune disease susceptibility.

Evidence that the Y chromosome influences autoimmune disease in male and female mice

Experimental allergic encephalomyelitis (EAE), an autoimmune model of multiple sclerosis, is a complex disease influenced by genetic, intrinsic, and environmental factors. In this study, we questioned whether parent-of-origin effects influence EAE, using reciprocal F2 intercross progeny generated between EAE-susceptible SJL/J (S) and EAE-resistant B10.S/SgMcdJ (B) mice. EAE susceptibility and severity were found to be different in female BS x BS intercross mice as compared with females from the three other birth crosses (BS x SB, SB x SB, and SB x BS), and in fact, both traits in female mice resembled those of their male siblings. This masculinization is associated with transmission of the SJL/J Y chromosome and an increased male-to-female sex ratio. Related studies using progeny of C57BL/6J Y-chromosome substitution strains demonstrate that the Y chromosome again influences EAE in both male and female mice, and that the disease course in females resembles that of their male littermates. Importantly, these data provide experimental evidence supporting the existence of a Y-chromosome polymorphism capable of modifying autoimmune disease susceptibility in both males and females.

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.

Serum IgM Repertoire Reactions to MBP/CFA Immunization Reflect the Individual Status of EAE Susceptibility

Lewis rats develop experimental allergic encephalomyelitis (EAE) in response to immunization with myelin basic protein (MBP) in CFA, while Fischer rats are usually resistant. These strains, while comparably producing anti-MBP antibodies, also differ in their repertoire reactions to immunization, as measured by patterns of serum IgM reactivity with various autologous proteins. We have now scored IgM repertoire reactions to MBP/CFA immunization after treatments that alter EAE susceptibility in either strain. The results show that abrogation of EAE susceptibility in Lewis rats by a previous experience of T cell-induced passive EAE provoked a novel set of IgM reactivities that otherwise characterized the Fischer's repertoire reaction. Conversely, these reactivities were delayed in the response of Fischer rats that had been rendered EAE-susceptible by cyclophosphamide. Another IgM reactivity with a significant association to individual EAE severity in Lewis rats behaved reciprocally. Together with previous results, these observations suggest that putative regulatory mechanisms concordantly affect EAE resistance and IgM repertoire reactions, operating naturally in Fischer rats and abrogatable by cyclophosphamide treatment, whereas naturally suppressed, but restorable in Lewis rats. Other treatments altering EAE susceptibility, however, did not share these characteristics and may thus be mediated by other mechanisms.

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

The relationship between the delayed-type hypersensitivity (DTH) response and susceptibility to experimental allergic encephalomyelitis (EAE) was examined using a unique age-dependent defect in the DTH response in an EAE-susceptible mouse strain. Young adult male SJL mice ( < 10 weeks of age) are defective in DTH responses following immunization with a variety of soluble antigens. By contrast, they respond to antigens applied to the skin, demonstrating a normal contact sensitivity response. In this report, we show that the non-responder male SJL are also unable to mount a DTH response to soluble neuroantigens or neuroantigens emulsified in complete adjuvant, and are additionally resistant to actively induced EAE. This contrasts with the DTH response in older males ( > 10 weeks of age) and young adult females (6 weeks of age), which are both DTH responders and susceptible to EAE. By contrast, all three groups are susceptible to EAE mediated by the transfer of activated effector T cells, suggesting that the defect in young adult males is in the induction of effectors. Furthermore, transfer of a macrophage population from female responders to young male non-responders mediates the induction of both DTH responsiveness and EAE susceptibility. The phenotype of this antigen-presenting cell is (I-A+, Mac-1+, Mac-2-, Mac-3+), identical to the phenotype of the macrophage regulating DTH responsiveness in this strain of mice. These data are consistent with the hypothesis that a defect in this cell inhibits induction of both CD4+Th1 DTH and EAE effector T cells.

Studies of experimental allergic encephalomyelitis in old mice

In old BALB/c mice susceptibility to experimental allergic encephalomyelitis (EAE) with bovine proteolipid apoprotein (PLP) is reduced significantly. Eleven of 21 8-week BALB/c mice developed clinical signs of EAE following injection of PLP but only two of 18 12-month BALB/c mice and one of 19 24-month BALB/c mice showed clinical signs of EAE. Susceptibility to EAE induced by either PLP or bovine myelin basic protein (MBP) also was reduced in old SJL mice. However, the aging process had no effect on the clinical signs of EAE in both strains, if EAE appeared. Some old BALB/c mice developed histologic EAE with signifcant demvelination without clinical signs. Lymphocyte proliferative response to mitogens and antigens, and interleukin-2 (IL-2) production, also were depressed in the aged mice (24-month BALB/c and 18-month SJL) probably due to the functional defct of T cells, since the function of macrophages as antigen-presenting cells was not affected in the old mice. PLP-sensitized spleen cells (SPC) from 8-week mice were able to adoptively transfer EAE to young and aged recipients. PLP-sensitized T cells from 8-week mice, reconstituted with young or old monocytes, also were able to transfer EAE into young mice. In contrast, spleen cells from aged mice did not induce EAE, so the reduction of EAE susceptibility was mainly explained by the failure of T cell activity. This T cell defect was not restored by exogenous IL-2.

Experimental allergic encephalomyelitis (EAE) in mice: primary control of EAE susceptibility is outside the H-2 complex.

We report here the results of EAE induction in 1758 mice from 9 inbred strains, 5 H-2 congenic strains, and 6 F1 hybrids. EAE responsiveness is under the primary control of genes outside the H-2 complex. The F1 data do not show a unifactorial inheritance of EAE responsiveness. The F1 data do imply a maternal factor, sex hormone, or sex-linked gene(s) that modifies EAE responsiveness. The data suggest that the H-2 complex modifies the degree of EAE responsiveness. This modulatory effect by H-2 could account for the contradictory reports in the literature on the association of H-2 type and EAE responsiveness.

Genetic control of susceptibility to experimental allergic encephalomyelitis in rats.

Rats of the inbred strains Lewis and DA are highly susceptible to the induction of experimental allergic encephalomyelitis (EAE) while Brown Norway rats are resistant to this disease. Evidence has been obtained which suggests that a single dominant gene is associated with susceptibility to EAE. The locus controlling EAE susceptibility is closely linked to the Ag-B histocompatibility locus but is not identical to it.