Abstract
Fas and Fas ligand (FasL) have been assigned a pivotal role for the development and maintenance of peripheral tolerance. Mice having defects in Fas and FasL develop lupus like symptoms. In this study, we have studied FasL expression of peripheral blood lymphocytes in patients with systemic lupus erythematosus (SLE) . Expression of FasL was not or very weakly detected in the freshly isolated PBMC in normal individuals. In contrast, freshly SLE PBMC exhibits enhanced expression of FasL withoutin vitrostimulation. Not only purified T cells but also purified B cells expressed FasL on their cell surface spontaneously in patients with SLE. Anti-DNA antibody secreting B cells were purified by using biotin labeled DNA and streptavidin-bead, and the freshly isolated anti-DNA autoantibody secreting B cells express FasL spontaneously. Thus autoreactive B lymphocytes that aberrantly express FasL would kill Fas+ immunoregulatory T lymphocytes. The aberrantly expressed FasL on B cells would, at least partly, facilitate escape of the autoreactive B cells from immune tolerance system, and may contribute sustained secretion of autoantibodies in patients with SLE.
