CD5-positive B cells at the crossroads of B cell malignancy and nonorgan-specific autoimmunity

The CD5 glycoprotein is detectable on a minute fraction of circulating B ce lls. The number of CD5(+) B cells (B1 cells) is increased in patients with autoimmune disorders and these cells, similar to those leading to chronic l ymphocytic leukemia (CLL), may be induced to produce multispecific autoanti bodies. CD5 is associated with the B cell antigen receptor, and the inducti on of apoptosis depends on the activation state of the cells. Defective reg ulation of this phenomenon might result in the production of autoantibodies and/or the development of CD5(+) B cell tumors. We have proposed that ther e may be different B1 populations in man, which depend on the consequence o f CD5 ligation on their surface: 'natural' or 'classical' CD5(+) B cells, a nd 'induced' CD5(+) B cells. (C) 2000 Editions scientifiques et medicales E lsevier SAS.