The study of the Ig variable region heavy chain (VH) genes used to encode antibodies specific for self-epitopes from murine hybridomas showed that three VH families are primarily utilized: VH J558, the largest family, and VH QPC52 and VH 7183, the families most proximal to the Ig joinin region heavy chain genes. These monoclonal autoantibodies express cross-reactive idiotopes shared by rheumatoid factors and antibodies specific for Sm. The expression of these idiotypes is independent of major histocompatibility complex and Ig constant region heavy chain haplotypes, self-antigen specificity, and even the VH gene family utilized.Though the experiments described here are limited to murine autoantibodies, similarities exist between murine and human autoimmune diseases. Studies that ain to investigate the relationship between VH gene expression and the presence of crossreactive idiotypes among human autoantibodies should enable us to better understand the mechanisms of autoimmunity and self-tolerance.

The F4 idiotype is a heavy chain determinant expressed almost exclusively on IgG immunoglobulins and is highly associated with specificity for double-stranded DNA. Since high-titered F4 expression is present predominantly in sera of patients with systemic lupus erythematosus (SLE), we thought F4ϩ IgG antibodies might constitute a useful subset of immunoglobulins in which to investigate lupus-specific alterations in variable (V) region gene expression or in the process of somatic mutation. This molecular analysis of F4 ϩ B cell lines generated from lupus patients demonstrates that despite the strong association of F4 reactivity with specificity for native DNA, there is no apparent V H gene restriction. Furthermore, V H gene segments encoding these antibodies are also used in protective immune responses.An examination of the process of somatic mutation in F4 ϩ antibodies showed no abnormality in frequency of somatic mutation nor in the distribution of mutations in complementarity-determining regions or framework regions. However, there was a decrease in targeting of mutations to putative mutational hot spots. This subtle difference in mutations present in these antibodies may reflect an intrinsic defect in mutational machinery or, more likely, altered state of B cell activation that affects the mutational process and perhaps also negative selection. (

No abstract

We report the molecular characterization of 2A4, an IgG, DNA-binding antibody bearing the 31 and F4 idiotypes which are associated with anti-DNA antibodies in serum of patients with systemic lupus erythematosus (SLE). The antibody is produced by an EBV-transformed B cell line derived from a patient with multiple myeloma whose myeloma protein is also an IgG, 31-reactive, F4-

We investigated the immunochemical and molecular characteristics of murine monoclonal rheumatoid factors. Study of the fine specificity of 20 monoclonal rheumatoid factor antibodies shows a wide degree of heterogeneity. However, many express an interstrain cross-reactive idiotype. We show that our rheumatoid factors utilize a restricted set of the heavy-chain variable region (VH) repertoire representing the more 3' VH families. Preferential expression of 3' VH families is known to occur early in development. We report the nucleotide sequence of two cloned rheumatoid factor VH genes, Y19-10 (VH J558) and 129-48 (VH 7183) in which no major differences are observed between VH genes encoding the heavy chain of autoantibodies and antibodies against foreign antigens.Antibodies directed against determinants of self IgG were first observed in the sera ofpatients with rheumatoid arthritis (1). Such antibodies, termed rheumatoid factors (RFs), can bind with a low affinity to the antigenic determinants expressed on the Fc fragment of autologous IgG (2). Later, RFs were found to be associated with various autoimmune diseases including systemic lupus erythematosus (3). The nature and origin of the RF response are still poorly understood. We have used murine RF monoclonal antibodies as models to study the immunochemical and molecular properties of autoantibodies. In this report, we present the following results. (i) Our monoclonal RFs, either spontaneous in nature or produced by induction, were predominantly of the ,u isotype and are multispecific. (ii) They express a high degree ofidiotype (Id) cross-reactivity, yet use different heavy-chain variable region (VH) gene segments. (iii) Regardless of their mouse strain origin, RFs use genes from a restricted number of VH gene families, namely J558, QPC52, and 7183. Sequence analysis revealed that the RF VH genes are closely related to germ-line genes that are used to encode antibodies to exogenous antigens. (iv) Id cross-reactivity may be due to a common tetrapeptide in framework 2 of the VH region.MATERIALS AND METHODS Animals. Six-month-old 129/Sv, 5-month-old MRL/lpr, and 3-month-old BALB/c mice, obtained from The Jackson Laboratory, were utilized in the preparation of hybridomas. Young adult female New Zealand White rabbits obtained from The Jackson Laboratory were used to prepare anti-Id antisera.Induction of RFs. BALB/c splenic lymphocytes cultured in RPMI supplemented with 20% (vol/vol) fetal calf serum were stimulated with Escherichia coli lipopolysaccharide (50 ,ug/ ml) for 4 days.