V sub(H) usage and somatic hypermutation in peripheral blood B cells of patients with rheumatoid arthritis (RA)

The human antibody repertoire has been demonstrated to have a marked V-gene-dependent bias that is conserved between individuals. In RA patients, certain heavy chain V genes (V sub(H)) have been found to be preferentially used for encoding autoantibodies. To determine if such preferential use of V sub(H) genes in autoantibodies is associated with a general distortion of the V gene repertoire in RA patients, the V sub(H) composition of peripheral blood B cells was analysed among four RA patients and four age- and sex-matched healthy controls. Usage of individual V sub(H) genes (eight V sub(H)3 and three V sub(H)4 genes tested by hybridization with a set of gene-specific oligonucleotide probes) was highly biased among RA patients, but no evidence of a distortion in the bias was observed compared with healthy controls. However, the occurrence of somatic mutations in these V sub(H) genes (estimated by differential hybridization with motif-specific oligonucleotide probes targeted to CDR and FR of the tested genes, and by DNA sequence analysis) was strikingly different between patients and healthy subjects. The number of V sub(H)3 rearrangements that had accumulated somatic mutations and the number of mutations per rearrangement were significantly elevated in three of the four RA patients. A slight but not significant elevation in mutations among rearranged V sub(H)4 genes was also observed in these patients. These data suggest that although usage of individual V sub(H) genes among peripheral blood B cells is not affected by the disease, the autoimmune process may involve a significant fraction of the B cell compartment.