A paralleled analysis of peripheral blood B cell populations applying next-generation sequencing revealed that CSF B cells seem to connect with memory B cells, DN B cells and plasmablasts, with DN B cells showing an intensive clonal relation to AQP4-specific CSF B cells . the CSF compartment, but also in B cell trafficking patterns across the BBB. In multiple sclerosis, CSF-specific B cell maturation, in combination with a bidirectional exchange of B cells across the BBB, is consistently detectable. These data suggest that B cells most likely encounter antigen(s) within the CSF and migrate across the BBB, with further maturation also taking place in the periphery. Autoantibody-mediated diseases, such as neuromyelitis optica spectrum disorder and LGI1 / NMDAR encephalitis, also show features of a CSF-specific B cell maturation and clonal connectivity with peripheral blood. In conclusion, these data suggest an intense exchange of B cells across the BBB, possibly feeding autoimmune circuits. Further developments in sequencing technologies will help to dissect the exact pathophysiologic mechanisms of B cells during neuro-inflammation. = 135) to exclude papers with non-neurological purposes such as lymphoma, glaucoma or leukemia. Preselected articles (= 75) were read in full-text. Articles were included in the systematic review using the following criteria: (1) the study included data on human research and not animal research, (2) the study displayed original data and did not report previously published data, or was a review of previous work or case report (reported patients = 1) and (3) the study methods stated sequencing of the B cell receptor. This search and inclusion criteria are described in the flowchart (Figure 1) and resulted in 38 articles selected for further analysis for the comprehensive review. In addition, we examined papers cited in the selected articles and included additional references based on their relevance regarding the scope of this paper. Due to the very inhomogeneous methodological approach between various studies (e.g., sequencing methods/platforms, CSF B cell subtypes studied and bioinformatics data processing used, patient selection) and limited sample sizes A1874 in the studies mentioned, no statistical meta-analysis could be conducted. Open in a separate window Figure 1 Workflow for the identification of studies. ** Records excluded after screening of abstract due to non-neurological purposes such as lymphoma, glaucoma or leukemia. 3. Results In order to learn more about B cell maturation and trafficking in neuro-inflammatory diseases, we performed the aforementioned search strategy and found several studies on B cell repertoire mass sequencing in multiple sclerosis and single studies on NMOSD as well as LGI1 and NMDAR autoantibody-mediated encephalitis. Early studies in MS with conventional B cell repertoire sequencing in the CSF compartment were also included in the analysis, in order to compare between the different methods and complete the picture A1874 of B cell pathophysiology in MS. B cell repertoire mass sequencing results in complex datasets; for this reason we ordered the A1874 results according to findings from basic repertoire analysis, clonal expansion within the CSF, B cell trafficking across the BBB andif availablelongitudinal CSF studies on single MS patients. 3.1. CSF B Cell Repertoires in Multiple Sclerosis The presence of oligoclonal bands (OCBs) still serve as important criteria in establishing the diagnosis of multiple sclerosis . Furthermore, OCBs and an intrathecal Ig synthesis have consistently been associated with elevated CSF B cell counts . During the last few decades, numerous studies further examined the role of CSF B cells by assessing B cell repertoires within the CSF, in lesions of MS patients  andmore recentlyin draining cervical lymph nodes . Although studies have not provided defined targets of CSF antibodies in MS yet, a deeper understanding of B cell trafficking, B A1874 Rabbit Polyclonal to C-RAF (phospho-Ser301) cell maturation and compartmentalized B cell reactions could be accomplished. 3.1.1. Enrichment of VH4 Family Usage in CSF B Cell Repertoires The basic analysis of B cell repertoire properties in the CSF of MS patients indicates that the VH germline usage of CSF B cells differs from the expected germline prevalence. Most studies on CSF B cell repertoires show a consistent shift towards an increased VH4 family usage (Table 1). In particular, the VH4 family members VH4-31, VH4-34, VH4-39, IGHV4-59 and IGHV4-61 [52,53,54,55,56], have been utilized in CSF B cell clones. In this context, CD138+ plasmablast/-cells show a more pronounced bias towards VH4 family usage than CD19+ B cells . An over-representation of VH4 in combination with VH2 families has been discussed in clinically isolated syndromes . These findings are in line with results from B cell repertoires derived from CNS MS lesions, which also found an over-representation of VH4 families [50,58,59,60,61], A1874 including VH4-34 and VH4-39 [51,58] family members. In addition,.