Th17 cells: A prognostic marker for MS rebound after natalizumab cessation?

BACKGROUND: Multiple sclerosis (MS) patients are at risk of renewed disease activity after discontinuing natalizumab (NAT) treatment. OBJECTIVE: Assessing the implication of T helper 17 (Th17) cells in MS reactivation after NAT cessation. METHODS: We monitored frequencies of Th17 cells and interleukin (IL)-17 cytokine levels in blood samples of 57 MS patients, without, during, and after NAT exposure. RESULTS: Frequencies of both Th17 cells and, in part, also IL-17 levels, in peripheral blood increased under prolonged NAT therapy, returned to baseline after NAT withdrawal and became almost undetectable in blood samples of individuals who experienced relapses during the wash-out phase. CONCLUSION: Assessing the Th17-cell/IL-17 axis might help to predict rebound MS activity after NAT withdrawal.

The Choroid Plexus Is Permissive for a Preactivated Antigen-Experienced Memory B-Cell Subset in Multiple Sclerosis.

The role of B cells in multiple sclerosis (MS) is increasingly recognized. B cells undergo compartmentalized redistribution in blood and cerebrospinal fluid (CSF) during active MS, whereby memory B cells accumulate in the CSF. While B-cell trafficking across the blood-brain barrier has been intensely investigated, cellular diapedesis through the blood-CSF barrier (BCSFB) is incompletely understood. To investigate how B cells interact with the choroid plexus to transmigrate into the CSF we isolated circulating B cells from healthy donors (HC) and MS patients, utilized an inverted cell culture filter system of human choroid plexus papilloma (HIBCPP) cells to determine transmigration rates of B-cell subsets, immunofluorescence, and electron microscopy to analyze migration routes, and qRT-PCR to determine cytokines/chemokines mediating B-cell diapedesis. We also screened the transcriptome of intrathecal B cells from MS patients. We found, that spontaneous transmigration of HC- and MS-derived B cells was scant, yet increased significantly in response to B-cell specific chemokines CXCL-12/CXCL-13, was further boosted upon pre-activation and occurred via paracellular and transcellular pathways. Migrating cells exhibited upregulation of several genes involved in B-cell activation/migration and enhanced expression of chemokine receptors CXCR4/CXCR5, and were predominantly of isotype class switched memory phenotype. This antigen-experienced migratory subset displayed more pronounced chemotactic activities in MS than in HC and was retrieved in intrathecal B cells from patients with active MS. Trafficking of class-switched memory B cells was downscaled in a small cohort of natalizumab-exposed MS patients and the proportions of these phenotypes were reduced in peripheral blood yet were enriched intrathecally in patients who experienced recurrence of disease activity after withdrawal of natalizumab. Our findings highlight the relevance of the BCSFB as important gate for the entry of potentially harmful activated B cells into the CSF.

Hypovitaminosis D upscales B-cell immunoreactivity in multiple sclerosis.

BACKGROUND: While vitamin D is increasingly recognized as a potential immune regulator of MS disease activity, its impact on B lymphocytes, however, remains ill-defined. METHODS: We assessed the impact of vitamin D on B-cell proliferation and cytokine secretion ex vivo and screened for effects of hypovitaminosis D and vitamin D supplementation on the compartmentalized distribution of B-cell subtypes in peripheral blood and cerebrospinal fluid (CSF) from patients with relapsing remitting MS (n=95) and various neurologic and healthy controls (n=57). RESULTS: B cells from MS patients with 25(OH)D serum levels <20ng/ml, displayed enhanced immunoreactivity ex vivo as a consequence of more vigorous responses of CD27(+) memory phenotypes. Immune responses decreased when B cells from either source were co-cultured in the presence of vitamin D or when retesting B cells from MS patients after prolonged supplementation with vitamin D. Hypovitaminosis D was detectable in the serum of 40/95 MS patients, correlated with decreased vitamin D concentrations in CSF and with higher disease activity, and was paralleled by intrathecal accumulation of CD27(+) B-cell subtypes and plasma cells. CONCLUSION: B-cell immunoreactivity is attenuated by vitamin D. Our finding that vitamin D deficiency affects the intrathecal compartment and coincides with increased frequencies of effector B-cell subtypes in the CSF suggests that hypovitaminosis D might contribute to augmenting disease activity in the target organ and supports a potential benefit of vitamin D supplementation in MS.