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

Abstract

A semiquantitative polymerase chain reaction (PCR) assay described in this study has been used to analyse the V_H1, V_H3 and V_H4 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_H4 gene family segments were preferentially underrepresented in IgM⁺ activated B cells. In IgG⁺ B cells the results suggest that V_H4 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_H4-specific B cell superantigen in the onset or development of SLE. This hypothesis is also supported by the sequence conservation of the fourth β loop—a putative superantigen binding site—of functional V_H4 gene segments which are preferentially used by anti-dsDNA lupus antibodies of established clones and hybridomas.

Full Text

The Full Text of this article is available as a PDF (828.1 KB).