Clonally expanded plasma cells in the cerebrospinal fluid of MS patients produce myelin‐specific antibodies

Abstract

Clonally expanded plasma cells (cePC) and their presumed products, oligoclonal immunoglobulin G bands (OCB), are characteristic findings in the cerebrospinal fluid (CSF) of patients with multiple sclerosis (MS). While cePC and OCB strongly suggest an involvement of B cell-dependent immune mechanisms in the pathogenesis of MS, their actual pathological relevance and target antigens remain unknown. To further understand the potential role played by cePC, we generated a panel of monoclonal antibodies (MS-mAb) from CSF-derived cePC from four patients with early or definite MS. Single-cell RT-PCR of correctly paired heavy and light chain immunoglobulin genes from individual cePC ensured the subsequent resurrection of their original antigen specificity. Immunofluorescence stainings of MS lesion tissue with MS-mAb revealed myelin reactivity in the cePC repertoire of all four patients and intracellular filament reactivity in one patient. While myelin staining by MS-mAb was only rarely detectable in non-MS CNS white matter tissue, it was greatly enhanced at the edge of demyelinating lesions in MS brain tissue. Our findings provide conclusive evidence for the presence of an antigen-driven B cell response in the CSF of MS patients directed against epitopes present in areas of myelin degradation.

NMDAR encephalitis: passive transfer from man to mouse by a recombinant antibody

“…All four treatment‐naive patients with recent onset anti‐NMDAR encephalitis in the current study showed intrathecal B‐cell and plasma cell accumulation and intrathecal production of NMDAR‐specific IgG. Moreover, using single‐cell RT‐PCR of FACS‐sorted CD138 + CSF plasma cells and recombinant antibody technology,19, 21 we identified expanded clones and were able to obtain seven different rhuMab (SSM1‐7) from intrathecal cePc of one of the anti‐NMDAR encephalitis patients. Ig sequences showed varying numbers of mutations from published germline sequences, indicating antigen‐driven expansion and ongoing somatic hypermutations.…”

“…To elucidate whether cePc are the actual source of the intrathecal autoantibody response, we cloned paired immunoglobulin heavy‐ and light‐chain variable gene regions from cePc essentially as previously described 19, 21. PEI mediated cotransfection of IgG‐HC and matching Ig‐LC expression vectors into FreeStyle 293‐F cells were carried out to produce recombinant monoclonal antibodies in vitro.…”

“…In this study, we focused on the analysis of clonally expanded intrathecal plasma cells (cePc), the cell population previously shown to be the main source of intrathecal immunoglobulin, often detectable as “oligoclonal bands.”18, 19 We determined whether cePc are responsible for anti‐NMDAR‐specific autoantibody production in patients with acute treatment‐naïve anti‐NMDAR encephalitis and whether these autoantibodies functionally interact with NMDAR in vitro and are indeed capable of eliciting core clinical symptoms of the disease in mice in vivo.…”

Antibodies in multiple sclerosis oligoclonal bands target debris

“…Some earlier studies that evaluated whole CSF IgG from MS patients identified antibodies to several different viruses, such as measles, varicella zoster, human T-lymphocytic virus 1, and human hepatitis virus 6 (7), whereas other investigations found antibodies targeting major myelin proteins, myelin basic protein (MBP) and myelin oligodencrocyte glycoprotein (MOG) (8,9) as well as glycolipids, fatty acids, and neurofilament proteins (10). Similarly, more recent investigations that have applied single-cell PCR cloning to individual CSF B cells in MS have detected antibodies to certain viruses or myelin proteins (11)(12)(13). However, it has been impossible to match specificity of antibodies identified in CSF to OCB by studying whole CSF IgG or recombinant antibodies constructed from rearranged Ig heavy-and light-chain genes in individual B cells.…”

Estimation of intrathecal IgG synthesis: simulation of the risk of underestimation

“…In other words, concentrations of intrathecally synthesized IgG may reach the required lower limit for biological activity in the CSF long before any ITS is detected. Moreover, antibodies directed to extracellular targets and with predictable biological activity are retained in brain tissues 29. Recent data suggest that autoreactive antibodies spilling over from the blood at a low level owing to an intact BCB may be completely cleared from the CSF by adsorption on CNS targets 30, 31…”