Accumulation of clonally related B lymphocytes in the cerebrospinal fluid of multiple sclerosis patients

The accumulation of B lymphocyte clones in the cerebrospinal fluid (CSF) of patients with multiple sclerosis (MS) and patients with other neurological disorders was investigated using PCR technologies. Oligoclonal B cell accumulations were detected in 10 of 10 MS patients, but only in 3 of 10 of the patients with other neurological disorders. Analyses of the Ig V(D)J sequences on the CSF from MS patients disclosed that V(H)3 and V(H)4 genes were extensively mutated compared with germline sequences, Moreover, a substantial proportion of the molecular clones analyzed shared the same third CDR of the ii chain variable region gene (HCDR3) and the same V-H genes, albeit with different numbers and locations of point mutations, thus indicating an ongoing process of intraclonal diversification. A larger number of clonally related V-H sequences could be obtained by using a V(H)3 gene-specific PCR so that genealogical trees depicting the process of diversification could be drawn. Analyses of the Ig V(D)J from the CSF of a patient with viral meningitis and oligoclonal B cell accumulations revealed that V(H)3 genes were extensively mutated, However, no intraclonal diversification could be observed even using V(H)3 gene-specific PCR methodologies. Clone-specific PCR and sequencing was used to detect the V(D)J found in the CSF of one MS patient in the PBL of the same patient. Only 1/3 of the V(D)J sequences investigated could be demonstrated in the PBL, indicating that the V(D)J genes utilized by B cells in the CSF are much less represented in the PBL. Collectively, the data suggest that in MS there is a compartmentalized clonal expansion.