Increased expression of c-rel, from the NF-κB/Rel family, in T cells from patients with systemic lupus erythematosus

Objective. To explore the role of the NF-κB/Rel transcription factor family in autoimmunity, we investigated whether peripheral blood mononuclear cells (PBMC) and T cells from the blood of patients with systemic lupus erythematosus (SLE) exhibit abnormal expression of c-rel, both when recently isolated and/or during in vitro activation. Methods. Total RNA and protein extracts were prepared from PBMC and T cells isolated by immunoadsorption with magnetic beads. The relative concentrations of c-rel mRNA and of c-Rel protein were determined by semiquantitative assays of competitive reverse transcriptase-polymerase chain reaction and chemiluminescent immunoblots, respectively. Activity of NF-κB/Rel was studied by electrophoretic mobility shift assay of nuclear extracts. Results. Significantly increased levels of c-rel mRNA were found (1) in PBMC from SLE patients (n = 48; p < 0.0000001), even during inactive disease (n = 11; p < 0.001), compared to controls (n = 54), and (2) in T cells isolated from a subgroup of these patients (n = 11; p < 0.00002) and controls (n = 12). c-Rel protein was found increased in the cytosol but not in the nucleus of PBMC of patients with SLE (n = 12; p < 0.02) compared to controls (n = 12). No evidence of NF-κB/Rel nuclear activity was detected. In vitro stimulation of T cells by incubating PBMC with concanavalin A showed that less c-Rel entered the nucleus in lupus cells than healthy cells, correlating with lower interleukin 2 production. However, the same stimulating conditions provoked an increase in c-rel mRNA to higher levels in lupus cells from 2 patients compared with 2 controls. Increased levels of both IκB α and IκB β could account for c-Rel cytosolic retention. Conclusion. Our data suggest that T cells from patients with SLE possess altered regulatory mechanisms of c-rel expression and nuclear import that might potentially determine conditions for developing autoimmunity. Other cells present in the PBMC could also be affected.