Expression of recombination activating genes 1 and 2 in peripheral B cells of patients with systemic lupus erythematosus

Objective. To analyze immunoregulatory abnormalities in patients with systemic lupus erythematosus (SLE) by assessing the expression of messenger RNA (mRNA) for types 1 and 2 recombination activating genes (RAG) in the peripheral blood of patients with active SLE. Methods. We examined B cell populations and also individual B cells from patients with SLE for the expression of RAG mRNA. Results. Analysis of bulk mRNA indicated that RAG1 and RAG2 mRNA were found routinely in peripheral B cells of patients with active SLE, but not in healthy subjects. When assessed on a single-cell basis, there was a 3-fold increase in the frequency of RAG1 and RAG2-expressing B cells in SLE patients compared with healthy subjects. Notably, B cells expressing both RAG1 and RAG2 mRNA expressed only IgD mRNA, but not IgG mRNA. Fifty percent of RAG-expressing B cells also expressed VpreB mRNA, whereas all expressed CD154 mRNA. Phenotypic analysis indicated that RAG-expressing B cells were activated, mature B cells. Conclusion. These results indicate that RAG expression is up-regulated in peripheral IgD+ and VpreB+ B cells of patients with active SLE. These cells may contribute to the immunoregulatory abnormalities in patients with SLE.