It is now unanimously accepted that autoimmunity could be defined as a breakdown of mechanisms responsible for self-tolerance. Among peripheral tolerance mechanisms, T cells anergy plays an important role. Previously, in patients with Systemic Lupus Erythematosus (SLE) it was demonstrated that peripheral T cells are resistant to anergy induction. Since some of E3 ubiquitin ligases (Cbl-b, GRAIL) are involved in T cells tolerance we initiated a study in order to establish the role of these ligases in SLE T cells anergy.

Our study included fifty eight SLE patients with active disease, forty nine with inactive disease and fifty healthy controls (HC). The patients were selected and characterized in Bucharest hospitals according to the American Rheumatism Association criteria. Cbl-b and GRAIL protein expression levels in peripheral blood mononuclear cells (PBMCs)/T cells were determined by western blotting using Cbl-b and GRAIL specific antibodies. The expression level of cbl-b mRNA in PBMCs/T cells was evaluated by RT-PCR. Cbl-b expression and distribution in T cells as well as its co-localization with lipid rafts was analyzed by confocal microscopy.

Both Cbl-b and GRAIL protein expression levels were significantly reduced in SLE, especially in patients with active disease, than in HC PBMCs. Also, a reduced level of Cbl-b mRNA was identified in active and inactive SLE T cells by comparison with HC. Confocal microscopy analysis confirmed these results showing that in SLE T cells Cbl-b has a reduced and diffuse expression and did not co-localize with preformed large lipid raft domains.

Our results suggested that abnormal expression of some E3 ligases could be involved in enhanced response of SLE T cells even if these are stimulated under anergic conditions.