Role of toll-like receptors and NKT cells in gene/environment interactions in a mouse model of multiple sclerosis

Miranda-Hernandez, Socorro (2013) Role of toll-like receptors and NKT cells in gene/environment interactions in a mouse model of multiple sclerosis. PhD thesis, James Cook University.

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Abstract

Multiple Sclerosis (MS) is a degenerative disease affecting the central nervous system. The molecular mechanisms and the development of therapies for MS are mainly studied in the animal model Experimental Autoimmune Encephalomyelitis (EAE), which is an induced demyelinating paralysis model, resembling some aspects of MS. Although significant advances have been achieved in MS and EAE, the genetic and environmental factors underlying the initiation and progression of MS are unclear and no curative or preventive therapies are known.

Toll-like receptors (TLRs) mediate the effects of some environmental factors in the immune system and initiate inflammatory responses against pathogen associated molecular patterns (PAMP) and danger associated molecular patterns (DAMP). Although studies show that TLR expression increases during MS and EAE in the CNS, the role of TLRs remains unclear in both diseases. In this study, it was examined the development of MOG₃₅₋₅₅/CFA + PTX–induced EAE in the absence of MyD88 and TLR1, TLR2, TLR4, TLR6, TLR9, TLR2/9 and TLR4/9. On the other hand regulatory cells such as NKT cells have been associated with inflammation in MS; nevertheless, the role of NKT cells in the disease is indistinct. In this study, it was examined the genetic control of NKT cell numbers in the severity of MOG₃₅₋₅₅/CFA + PTX–induced EAE.

C57BL/6 mice developed a chronic form of MOG₃₅₋₅₅/CFA + PTX–induced EAE. The absence of TLR1, TLR4, TLR6 and TLR4/9 did not affect the severity of chronic active MOG₃₅₋₅₅/CFA + PTX–induced EAE in C57BL/6 mice; however, C57BL/6.Myd88⁻/⁻ mice were completely protected from the disease. Female C57BL/6.Tlr2⁻/⁻ and C57BL/6.Tlr9⁻/⁻ mice showed less severe clinical signs of MOG₃₅₋₅₅/CFA + PTX–induced EAE compared with wild type (WT) B6 mice. C57BL/6.Tlr2⁻/⁻9⁻/⁻ male and females mice also decreased the severity of MOG₃₅₋₅₅/CFA + PTX–induced EAE compared with WT B6 mice but the disease was not less severe that that seen in single deficient female mice in TLR2 or TLR9.

The passive form of chronic MOG₃₅₋₅₅/CFA + PTX–induced EAE confirmed protection from disease in the absence of TLR2 and TLR9. Passive MOG₃₅₋₅₅/CFA + PTX–induced EAE was ameliorated in C57BL/6.Tlr9⁻/⁻ female mice but the clinical signs of disease were similar to those seen in active MOG₃₅₋₅₅/CFA + PTX–induced EAE. However, both male and female C57BL/6.Tlr2⁻/⁻ mice were completely protected. Protection of disease in the absence of TLR2 was associated with fewer CNS-infiltrating CD4⁺ T cells, fewer CNS-infiltrating CD4⁺ T cells secreting IL17, increasing proportions of central (CD62L⁺) CD4⁺CD25⁺Foxp3⁺ regulatory T cells and reduced prevalence of detectable circulating levels of IL6.

As type 1 diabetes (T1D)-prone NOD mice are susceptible to MOG₃₅₋₅₅/CFA + PTX–induced EAE, we used the same approach to study MOG₃₅₋₅₅/CFA + PTX–induced EAE in this strain in order to dissect the interrelationships between organ-specific autoimmune diseases. NOD mice showed a mild form of relapsing-remitting MOG₃₅₋₅₅/CFA + PTX–induced EAE. The absence of TLR1, TLR2, TLR4, TLR6 and TLR9 did not affect the clinical course of relapsing remitting MOG₃₅₋₅₅/CFA + PTX–induced EAE in both males and female mice compared to the WT NOD/Lt controls. As the absence of TLR2 did not decrease the severity of MOG₃₅₋₅₅/CFA + PTX–induced EAE in NOD mice, it was hypothesized that insulitis associated with T1D development in some way compensated for the lack of TLR2 signalling in NOD mice. To test this hypothesis, NOD/Lt mice carrying the MHC haplotype H2ᵇ from C57BL/6 mice (NOD.H2ᵇ) were crossed onto the NOD.Tlr2⁻/⁻ strain. NOD.H2ᵇ mice were completely protected from T1D and insulitis but showed more severe relapsing remitting MOG₃₅₋₅₅/CFA + PTX–induced EAE than NOD/Lt mice. In contrast, the severity of relapsing remitting MOG₃₅₋₅₅/CFA + PTX–induced EAE decreased in NOD.H2ᵇ.Tlr2-/- mice. Moreover, NOD.H2ᵇ.Tlr2⁻/⁻ mice were protected from relapses of MOG₃₅₋₅₅/CFA + PTX–induced EAE. This data suggest that both TLR2 signalling and immunological events associated with autoimmunity at distant site can mediate relapses in CNS autoimmunity.

Because mice with increased numbers of NKT cells are protected from T1D and NKT cells have been associated with both increase severity and decrease severity of MS. In this study, it was hypothesized that genetic control of NKT cells numbers affects the severity of MOG₃₅₋₅₅/CFA + PTX–induced EAE. The clinical course of active MOG₃₅₋₅₅/CFA + PTX– induced EAE was not affected in NOD/Lt congenic mice for Nkrp1b, NKT1, NKT2a, NKT2b and NKT2e. The absence of Cd1d did not affect the severity of MOG₃₅₋₅₅/CFA + PTX–induced EAE neither in C57BL/6 mice nor in NOD/Lt mice. NOD.Idd13 mice showed an increased severity of MOG₃₅₋₅₅/CFA + PTX–induced EAE. Transgenic C57BL/6.Tg(mCD4-Vα14)6 female mice but not male mice ameliorated the severity of MOG₃₅₋₅₅/CFA + PTX–induced EAE. Both male and female C57BL/6.Tg(mCD4-Vα14)5 decreased the severity of MOG₃₅₋₅₅/CFA + PTX–induced EAE. C57BL/6.Tg(mCD4-Vα14)2 female were completely protected but not males. These data indicate that increased numbers of NKT cells play a role in CNS autoimmune inflammation.

In conclusion, these results indicate that signalling provided by TLR9 play a partial role in the severity of CNS autoimmunity. The effector phase of autoimmune inflammation in the CNS is dependent of TLR2 signalling. Genetic control of NKT numbers is associated with the severity of autoimmune CNS inflammation.

Item ID: 35564
Item Type: Thesis (PhD)
Keywords: autoimmune diseases; diabetes; disseminated sclerosis; EAE; encephalomyelitis disseminate; Experimental Autoimmune Encephalomyelitis; immune system disorders; MS; multiple sclerosis; nervous system disorders; TLRs; toll-like receptors
Additional Information:

Publications arising from this thesis are available from the Related URLs field. The publications are:

Miranda-Hernandez, Socorro, Gerlach, Nicole, Fletcher, Julie M., Biros, Erik, Mack, Matthias , Körner, Heinrich, and Baxter, Alan G. (2011) Role for MyD88, TLR2 and TLR9 but not TLR1, TLR4 or TLR6 in experimental autoimmune encephalomyelitis. Journal of Immunology, 187 (2). pp. 791-804.

Miranda-Hernandez, Socorro, and Baxter, Alan (2013) Role of toll-like receptors in multiple sclerosis. American Journal of Clinical and Experimental Immunology, 2 (1). pp. 75-93.

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Date Deposited: 20 Nov 2014 02:14
FoR Codes: 06 BIOLOGICAL SCIENCES > 0601 Biochemistry and Cell Biology > 060110 Receptors and Membrane Biology @ 50%
06 BIOLOGICAL SCIENCES > 0601 Biochemistry and Cell Biology > 060199 Biochemistry and Cell Biology not elsewhere classified @ 50%
SEO Codes: 92 HEALTH > 9201 Clinical Health (Organs, Diseases and Abnormal Conditions) > 920111 Nervous System and Disorders @ 34%
92 HEALTH > 9201 Clinical Health (Organs, Diseases and Abnormal Conditions) > 920108 Immune System and Allergy @ 33%
92 HEALTH > 9201 Clinical Health (Organs, Diseases and Abnormal Conditions) > 920104 Diabetes @ 33%
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