Pre-B lymphocytes with intracytoplasmic mu chains in the peripheral blood of rheumatoid arthritis patients

A dysregulation of B-cell differentiation and activation has long been evidenced in rheumatoid arthritis (RA). Such analyses have, however, usually focused on the latest stages of B-cell development. Using a classical technique of immunofluorescence labeling on cytospins, we investigated the presence of peripheral pre-B lymphocytes in 92 RA patients and 23 controls. Cells with intracytoplasmic mu chains were evidenced in 58.7% of the RA patients studied, ranging between 0 and 30%, while small numbers of c-mu cells, never exceeding 6% of peripheral blood lymphocytes, were observed in 9 controls. Relationships between this feature and clinical or laboratory data were investigated, showing a negative correlation between the percentage of c-mu + lymphocytes and Ritchie's index (P = 0.05), the number of tender or swollen joints (P = 0.05), erythrocyte sedimentation rate (P = 0.005), seropositivity (P = 0.05), and disease duration (P = 0.01).