VH4 Gene Segments Dominate the Intrathecal Humoral Immune Response in Multiple Sclerosis

Abstract

A characteristic feature of the CNS inflammatory response in multiple sclerosis (MS) is the intrathecal synthesis of IgG and the presence of oligoclonal bands. A strong correlation between CD138+ plasma blast numbers in MS cerebrospinal fluid (CeSF) and intrathecal IgG synthesis suggests that these cells are the major Ab-secreting cell type in MS CeSF. Sequencing of V regions from CD138+ cells in MS CeSF has revealed somatically mutated and expanded IgG clonotypes consistent with an Ag-targeted response. In the present study, single-cell RT-PCR analysis of CD138+ cells from 11 MS patients representing differing clinical courses and stages of disease identified expansion of CD138+ cells with functionally rearranged VH4 gene segments as an overriding feature of MS CeSF repertoires. VH4 dominance was attributed to the preferential selection of specific VH4 genes, particularly gene segment VH4-39, which displayed a significant enrichment in CeSF compared with MS peripheral blood B cells. A modest increase in VH4 prevalence among MS peripheral blood IgG memory cells was also noted, suggesting that factors shaping the CD138 repertoire in CeSF might also influence the peripheral IgG memory cell pool. These results indicate a highly restricted B cell response in MS. Identifying the targets of CeSF plasma cells may yield insights into disease pathogenesis.

CSF IgG heavy-chain bias in patients at the time of a clinically isolated syndrome

“…The CSF CD138 plasma cell VH family distribution deviated from germline frequencies, however, in 7 of 8 CIS subjects (Table 3). As previously observed in MS CD138 plasma cell repertoires (Owens et al, 2007b), CD138 VH family germline bias was not driven by clonal expansion as only 2 of 8 VH family germline distributions differed when tabulated by total or unique sequences. For subject ON04-7, the discrepancy between the total and unique CD138 plasma cell distributions was due to the high percentage of sequences in clonal populations (85%) and the limited number of unique sequences available for analysis.…”

“…As observed in MS plaque (Owens et al, 1998) and CSF (Owens et al, 2007b), the bias in the B and plasma cell IgG VH family distributions were due to an overrepresentation of VH4 and sometimes VH2 family germline sequences (Tables 3 and 4). In 3 (ON03-1, ON03-4, and ON04-10) of 10 subjects, the V H family distribution in the CSF IgG B or plasma cell repertoire did not vary statistically from family germline prevalence (Cook and Tomlinson, 1995).…”

“…CSF IgG repertoire bias has not been extensively investigated in other inflammatory CNS disorders; however, VH segments recovered from subacute sclerosing panenchephalitis CSF reveal an excess of VH1 rather than VH4 family segments (Owens et al, 2007a;Owens et al, 2007b). This suggests that compartmental VH4 or VH2 repertoire bias may not be a phenomenon of general CNS inflammation but have specific relevance to MS.…”

“…Interestingly, the two germlines that are overrepresented in CIS subjects, VH4 and VH2, are closely related based on nucleotide sequence homology in the framework 1 and framework 3 intervals (Kirkham et al, 1992). Since VH4 repertoire bias is evident in established demyelinating disease (Owens et al, 2007b), the early presence of VH4 bias at the time of CIS may indicate that the target of the humoral immune response does not change significantly over time. This hypothesis, however, needs to be examined further by longitudinal analysis of MS B and plasma cell VH repertoires.…”

“…An additional feature of the central nervous system (CNS) IgG repertoire in MS patients is the overrepresentation of VH4 family heavy chain sequences in MS plaque, periplaque white matter, and CSF (Baranzini et al, 1999;Owens et al, 1998;Owens et al, 2007b;Smith-Jensen et al, 2000). The temporal course of VH4 bias in MS remains unknown.…”