Objective: Defective regulation of programmed cell death (apoptosis) may play a role in the development of autoimmune diseases, and the proto-oncogene bcl-2 is involved in the control of apoptosis in immunocompetent cells. We therefore wished to investigate the expression of bcl-2 in the peripheral lymphocytes of patients with systemic lupus erythematosus (SLE), a prototypical autoimmune disease.
Methods: Levels of bcl-2 expression in the lymphocytes of patients with SLE and, for comparison, in the lymphocytes of healthy controls and patients with rheumatoid arthritis (RA), systemic bacterial infections, and chronic B cell lymphocytic leukemia were studied by 2-color cytofluorography and RNA analysis.
Results: In SLE patients, a significant proportion of T cells expressed increased amounts of bcl-2 protein. By fluorescence-activated cell sorter analysis, bcl-2--enriched lymphocytes were found in the CD45RO+ as well as in the CD45RO-, and also in the CD4+ and CD8+, lymphocyte subpopulations. Mononuclear cells of patients with SLE showed increased amounts of bcl-2 messenger RNA. An increased percentage of strongly bcl-2 positive peripheral T lymphocytes was found in patients with bacterial infections, but not in those with RA.
Conclusion: Although the occurrence of circulating T lymphocytes with abnormally high bcl-2 expression is not specific for SLE, it is evidence for a dysregulation of lymphocytic programmed cell death in this autoimmune disease.