Perforin-2 is overexpressed in Kikuchi-Fujimoto disease

Kikuchi-Fujimoto disease (KFD) is a self-limited lymphadenopathy characterized by subcortical necrosis and paracortical proliferation of lymphocytes, histiocytes and plasmacytoid dendritic cells with abundant apoptosis. The etiology of KFD remains unknown. Perforin-2 is a highly conserved transmembrane molecule capable of forming pores following intercellular interaction with bacteria and erythrocytes. Perforin-2 is also essential for the activation of type I interferon-induced JAK/STAT signaling and elimination of virus infection. Herein, we hypothesized that perforin-2 or macrophage-expressed gene 1 (MPEG1) protein function is dysregulated in KFD, resulting in an exaggerated immune response, possibly following exposure to an unknown infectious agent. Twelve cases of KFD were the study group. We isolated total RNA from fixed, paraffin-embedded whole tissue sections. We also assessed primary human B-cells and 4 cases of reactive follicular hyperplasia as controls. Perforin-2 mRNA levels were assessed by quantitative real-time PCR (qRT-PCR). We found that perforin-2 mRNA expression was significantly upregulated in 11 of 12 (92%) KFD cases as compared with control samples. These results suggest that expression of perforin-2 is dramatically upregulated in KFD cases. Increased levels of perforin-2 likely explain the abundant apoptosis in KFD. These data also support the hypothesis that upregulation of perforin-2 may be part of the host immune reaction to an unknown infectious agent that is the trigger for KFD.