Lack of junctional adhesion molecule (JAM)-B ameliorates experimental autoimmune encephalomyelitis

Abstract

In multiple sclerosis (MS) and its animal model experimental autoimmune encephalomyelitis (EAE) autoaggressive CD4 T cells cross the blood-brain barrier (BBB) and cause neuroinflammation. Therapeutic targeting of CD4 T-cell trafficking into the CNS by blocking α4-integrins has proven beneficial for the treatment of MS but comes with associated risks, probably due to blocking CD8 T cell mediated CNS immune surveillance. Our recent observations show that CD8 T cells also rely on α4β1-integrins to cross the BBB. Besides vascular cell adhesion molecule-1 (VCAM-1), we identified junctional adhesion molecule-B (JAM-B) as a novel vascular α4β1-integrin ligand involved in CD8 T-cell migration across the BBB. This prompted us to investigate, if JAM-B also mediates CD4 T-cell migration across the BBB. We first ensured that encephalitogenic T cells can bind to JAM-B in vitro and next compared EAE pathogenesis in JAM-B C57BL/6J mice and their wild-type littermates. Following immunization with MOG peptide, JAM-B mice developed ameliorated EAE compared to their wild-type littermates. At the same time, we isolated higher numbers of CD45 infiltrating immune cells from the CNS of JAM-B C57BL/6J mice suffering from EAE. Immunofluorescence staining revealed that the majority of CD45 inflammatory cells accumulated in the leptomeningeal and perivascular spaces of the CNS behind the BBB but do not gain access to the CNS parenchyma. Trapping of CNS inflammatory cells was not due to increased inflammatory cell proliferation. Neither a loss of BBB integrity or BBB polarity potentially affecting local chemokine gradients nor a lack of focal gelatinase activation required for CNS parenchymal immune cell entry across the glia limitans could be detected in JAM-B mice. Lack of a role for JAM-B in the effector phase of EAE was supported by the observation that we did not detect any role for JAM-B in EAE pathogenesis, when EAE was elicited by in vitro activated MOG specific CD4 effector T cells. On the other hand, we also failed to demonstrate any role of JAM-B in in vivo priming, proliferation or polarization of MOG-specific CD4 T cells in peripheral immune organs. Finally, our study excludes expression of and thus a role for JAM-B on peripheral and CNS infiltrating myeloid cells. Taken together, although endothelial JAM-B is not required for immune cell trafficking across the BBB in EAE, in its absence accumulation of inflammatory cells mainly in CNS leptomeningeal spaces leads to amelioration of EAE.

Novel Blood-Derived Extracellular Vesicle-Based Biomarkers in Alzheimer’s Disease Identified by Proximity Extension Assay

“…We did not detect any differences in plasma; however, EVs depicted a similar difference of JAM-B, as that seen in the study by Whelan et al [ 59 ], where JAM-B was found downregulated in cognitively affected. JAM-B is a tight junction protein expressed by brain endothelial cells forming the BBB [ 60 ], and its dysregulation could be ascribed to the disruption of the BBB [ 61 ]. JAM-B has also been associated with lymphocyte transendothelial migration [ 62 ] and vascular inflammation [ 63 ].…”

Immune cell trafficking across the blood-brain barrier in the absence and presence of neuroinflammation

“…JAMs are immunoglobulin superfamily transmembrane proteins, with JAM-A and JAM-B being the most studied in BBB endothelial cells. JAM-A contributes to the establishment of cell polarity (22) and both JAM-A and JAM-B have been described to mediate leukocyte trafficking across the BBB (23,24,25,26,27) (summarized in (10)). Tricellular contact points between BBB endothelial cells show localization of tricellulin, which otherwise has only been described in epithelial tricellular junctions.…”

“…The crucial role played by α 4 β 1 /VCAM-1 interaction in T-cell arrest on the BBB is highlighted by the fact that blocking α 4 -integrins has been translated into the most effective treatment for relapsing-remitting MS with the humanized monoclonal anti-α 4 integrin antibody natalizumab. In addition to VCAM-1, another endothelial ligand for α 4 β 1 integrin, namely JAM-B has been shown to be involved in CD8 + ( 27 ), but not CD4 + ( 24 ) T-cell migration across the BBB in mouse models.…”

Functional relevance of the multi-drug transporter abcg2 on teriflunomide therapy in an animal model of multiple sclerosis

“…In vitro-treated cells or cells from in vivo-treated mice were stimulated with 50 ng/mL phorbol myristate acetate (PMA; Alexix Biochemicals), 1 mg/mL ionomycin (BioVision, Inc.), and 3.3 μl/5 mL GolgiStop (BD Biosciences) for 4 h at 37°C in 5 mL medium. After stimulation, cells were collected and stained for CD4, CD25, and FoxP3 using the Treg Detection Kit according to manufacturer's protocol (Myltenyi) or for intracellular cytokines (IFN-γ, IL-17, GM-CSF, IL-4, IL-10) and surface markers (CD45, CD4, CD8) as adapted from [16]. For surface staining, cells were incubated with primary antibody (Additional file 6: Table S1) mixes in FACS buffer (DPBS, 2.5% FBS, and 0.1% NaN 3 ) for 30 min on ice.…”