Naive B cells expressing IgM and IgD on their surface have no or little somatic mutations in V genes. We have demonstrated that the human IgM⁺IgD⁺B cell clone (0 – 81), which expresses nephritogenic idiotypes, produces IgM anti‐DNA antibodies which show monospecificity to DNA. Using a DNA probe which specifically links to the V_H gene of antibody 0 – 81, we identified the counterpart germ‐line V gene of 0 – 81, V3‐7, which appears to be used by pathogenic autoantibodies in humans. Clone 0 – 81, which may belong to naive B cells in terms of cell phenotype, uses a somatically mutated V3‐7 gene. We further studied DNA sequences of V3‐7 genes in circulating IgM⁺IgD⁺B cells from normal subjects and patients with systemic lupus erythematosus (SLE). The results revealed that rearranged V3‐7 genes in IgM⁺IgD⁺B cells from patients with SLE contained somatically mutated sequences at significantly increased frequencies. These data indicate an abnormal maturation of B cells in autoimmune states that may be associated with an escape of self‐reactive B cells from the elimination process in the germinal center.