Differential abnormality in cell-cycle stage of peripheral B cells from patients with systemic lupus erythematosus

In order to clarify the stage of abnormal activation of systemic lupus erythematosus (SLE) B cells, we investigated the cell-cycle phase of SLE B cells by flow-cytometric analysis. This study uses the simultaneous flow-cytometric analysis of cellular DNA content and incorporated bromodeoxyuridine, an analogue of thymidine, as indicators for DNA synthesis to detect activated B cells in peripheral blood of patients with SLE. In active SLE, the percentage of B cells increased in the S and G2M phase and decreased in the G0G1 phase as compared with normal control subjects. In inactive SLE, the percentage of B cells in the S phase also increased. Active SLE B cells did not progress through the cell cycle with the stimulation of anti-IgM plus PMA or SAC plus BSF, although normal B cells transit into S and G2M phase with such stimulation. These data suggest that SLE B cells are already activated and shifted to a matured state and that for this reason the B cells were poorly responsive to mitogen.