Demethylation of ITGAL (CD11a) regulatory sequences in systemic lupus erythematosus

Objective. Inhibition of T cell DNA methylation causes autoreactivity in vitro and a lupus-like disease in vivo, suggesting that T cell DNA hypomethylation may contribute to autoimmunity. The hypomethylation effects are due, in part, to overexpression of lymphocyte function-associated antigen 1 (LFA-1) (CD11a/CD18). Importantly, T cells from patients with active lupus have hypomethylated DNA and overexpress LFA-1 on an autoreactive subset, suggesting that the same mechanism could contribute to human lupus. The present study investigated the nature of the methylation change that affects LFA-1 expression in vitro and in human lupus. Methods. Bisulfite sequencing was used to determine the methylation status of the ITGAL promoter and flanking regions in T cells from lupus patients and healthy subjects, and in T cells treated with DNA methylation inhibitors. "Patch" methylation of promoter sequences in reporter constructs was used to determine the functional significance of the methylation changes. Results. Hypomethylation of specific sequences flanking the ITGAL promoter was seen in T cells from patients with active lupus and in T cells treated with 5-azacytidine and procainamide. Patch methylation of this region suppressed ITGAL promoter function. Conclusion. DNA methylation changes occur in specific sequences that regulate LFA-1 expression in lupus T cells and in the hypomethylation model, indicating that altered methylation of specific genes may play a role in the pathogenesis of lupus.