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* Department of Medicine, University of Michigan, and
Department of Medicine, Ann Arbor Veterans Affairs Medical Center, Ann Arbor, MI 48109
Inhibiting DNA methylation in CD4+ T cells causes aberrant gene expression and autoreactive monocyte/macrophage killing in vitro, and the hypomethylated cells cause a lupus-like disease in animal models. Similar decreases in T cell DNA methylation occur in idiopathic lupus, potentially contributing to disease pathogenesis. The genes affected by DNA hypomethylation are largely unknown. Using DNA methylation inhibitors and oligonucleotide arrays we have identified perforin as a methylation-sensitive gene. Our group has also reported that DNA methylation inhibitors increase CD4+ T cell perforin by demethylating a conserved methylation-sensitive region that is hypomethylated in primary CD8+ cells, which express perforin, but is largely methylated in primary CD4+ cells, which do not. As lupus T cells also have hypomethylated DNA and promiscuously kill autologous monocytes/macrophages, we hypothesized that perforin may be similarly overexpressed in lupus T cells and contribute to the monocyte killing. We report that CD4+ T cells from patients with active, but not inactive, lupus overexpress perforin, and that overexpression is related to demethylation of the same sequences suppressing perforin transcription in primary CD4+ T cells and demethylated by DNA methylation inhibitors. Further, the perforin inhibitor concanamycin A blocks autologous monocyte killing by CD4+ lupus T cells, suggesting that the perforin is functional. We conclude that demethylation of specific regulatory elements contributes to perforin overexpression in CD4+ lupus T cells. Our results also suggest that aberrant perforin expression in CD4+ lupus T cells may contribute to monocyte killing.
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