DC-SIGN association with the Th2 environment of lepromatous lesions: cause or effect?

The clinical spectrum of leprosy is related to patients' immune responses. Non‐responsiveness towards Mycobacterium leprae (ML) seems to correlate with a Th2 cytokine profile. The reason for such a polarized immune response remains unclear. The C‐type lectin, DC‐SIGN, expressed by subsets of dendritic cells (DCs) and macrophages, has previously been associated with Th2 responses. Here we show abundant DC‐SIGN expression in lepromatous but not borderline tuberculoid leprosy, in both HIV‐positive and HIV‐negative patients. Moreover, we demonstrate that DC‐SIGN can act as an entry receptor for ML, as it does for M. tuberculosis, through the cell wall component lipoarabinomannan. DC‐SIGN is expressed on virtually all ML‐containing cells, providing further evidence for its role as a receptor. DC‐SIGN may therefore be induced on macrophages in lepromatous leprosy and may then contribute to mycobacterial entry into these cells. Copyright © 2006 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.