Defective expression and function of the ILT2/CD85j regulatory receptor in dendritic cells from patients with systemic lupus erythematosus

Dendritic cells (DCs) play an important role in inducing immune tolerance. Inhibitory receptors, such as ILT2/CD85j, are involved in the tolerogenic effect of DCs and previous studies have indicated the important role of these receptors on the pathogenesis of autoimmune diseases. The aim of this study was to evaluate the expression and function of ILT2 in DCs from SLE patients. Peripheral blood from fifty patients with SLE and 38 healthy volunteers was obtained. ILT2 expression was assessed by flow cytometry. DCs were generated in the absence or presence of an anti-ILT2 antibody. The effect of ILT2 in the immunogenic ability of SLE DCs was also evaluated. We observed that SLE patients had significant higher levels of circulating plasmacytoid DCs (pDCs), and that these levels correlated with disease activity. In contrast, the expression of ILT2 was diminished in both pDCs and myeloid DCs (mDCs) from these patients. However, under our experimental conditions, the in vitro differentiation of DCs was not apparently affected by ILT2 engagement. In contrast, the immunogenic capability of monocyte-derived DCs was not down-regulated by ILT2 cross-linking in a significant proportion of SLE patients. Our results suggest that ILT2 participates in the defective immune-regulation observed in patients with SLE.