V(H) gene-family representation in peripheral activated B cells from systemic lupus erythematosus (SLE) patients

A semiquantitative polymerase chain reaction (PCR) assay described in this study has been used to analyse the V(H)1, V(H)3 and V(H)4 repertoire expressed by total IgM+ and IgG+ B cells from normal individuals and lupus patients. This approach consists of a combination of B cell selection, utilization of the anchored PCR technique to avoid technical bias in the amplification of different V(H) gene family cDNA templates, and screening of the amplified IgM or IgG cDNA rearrangements by family-specific oligonucleotide probes. In four lupus patients, V(H) family representation in IgM+ and IgG+ in vivo activated B cells, selected by anti-CD71 antibody, and in total CD19+ B cells were compared. In all patients, V(H)4 gene family segments were preferentially under-represented in IgM+ activated B cells. In IgG+ B cells the results suggest that V(H)4 expression is variable, depending on the phase of the disease. Polyclonal B cell activation, which is usually considered as being the first event in autoantibody production in SLE, cannot explain our results. The data evoke the possible involvement of a V(H)4-specific B cell superantigen in the onset or development of SLE. This hypothesis is also supported by the sequence conservation of the fourth beta loop a putative superantigen binding site of functional V(H)4 gene segments which are preferentially used by anti-dsDNA lupus antibodies of established clones and hybridomas.