Immunization with Recombinantly Expressed LRP4 Induces Experimental Autoimmune Myasthenia Gravis in C57BL/6 Mice

Background: Myasthenia gravis (MG) is an autoimmune disease of the neuromuscular junction (NMJ), characterized with muscle weakness. While MG develops due to acetylcholine receptor (AChR) antibodies in most patients, antibodies to muscle-specific receptor tyrosine kinase (MuSK) or low-density lipoprotein receptor-related protein 4 (LRP4) may also be identified. Experimental autoimmune myasthenia gravis (EAMG) has been previously induced by both LRP4 immunization and passive transfer of LRP4 antibodies.Objective: Our aim was to confirm previous results and to test the pathogenic effects of LRP4 immunization in a commonly used mouse strain C57BL/6 (B6) using a recombinantly expressed human LRP4 protein.Methods: B6 mice were immunized with human LRP4 in CFA, Torpedo Californica AChR in CFA or only CFA. Clinical and pathogenic aspects of EAMG were compared among groups.Results: LRP4- and AChR-immunized mice showed comparable EAMG clinical severity. LRP4-immunized mice displayed serum antibodies to LRP4 and NMJ IgG and complement factor C3 deposits. IgG2 was the dominant anti-LRP4 isotype. Cultured lymph node cells of LRP4- and AChR-immunized mice gave identical pro-inflammatory cytokine (IL-6, IFN- and IL-17) responses to LRP4 and AChR stimulation, respectively.Conclusion: Our results confirm the EAMG-inducing action of LRP4 immunization and identify B6 as a LRP4-EAMG-susceptible mouse strain. Demonstration of complement fixing anti-LRP4 antibodies in sera and complement/IgG deposits at the NMJ of LRP4-immunized mice indicates complement activation as a putative pathogenic mechanism. We have thus developed a practical LRP4-induced EAMG model using a non-conformational protein and a widely available mouse strain for future investigation of LRP4-related MG

The role of pericytes in MS pathophysiology.

Objective:Our aim was to investigate the impact of pericytes, an important component of the blood brain barrier (BBB), on multiple sclerosis (MS) pathogenesis.Background:Although MS is known as a classical inflammatory demyelinating disorder, the involvement of glial cells in demyelination is increasingly recognized. Vascular pathology has also been recently found to contribute to the pathogenesis of MS. However, the exact mechanisms of this pathology and the influence of pericytes have been scarcely investigated.Design/Methods:Experimental allergic encephalomyelitis (EAE) was induced in C57BL6 mice by myelin oligodendrocyte glycoprotein (MOG) immunization. BBB permeability, number and localization of pericytes were assessed in MS lesions and extracellular matrix components were investigated by immunohistochemical methods.Results:Multiple inflammatory lesions were detected in spinal cord and brain on 40thday of MOG-induced EAE. The lesions contained an abundance of T cells and macrophages and lacked myelin. The BBB permeability increase was shown on EAE lesions by albumin staining. The lesion sites with albumin leakage showed a reduction in PDGFRB+ pericytes and some of the pericytes were found to deviate from the walls of microvessels and be repositioned in the brain parenchyma. Moreover, aSMA+ cells and the extracellular matrix protein content around PDGFRB+ and aSMA+ cells were significantly increased.Conclusions:In this study, we have shown for the first time that EAE lesions show altered pericyte distribution. This alteration is associated with a change in BBB permeability and an increase in extracellular matrix