Cantharidin modulates development of human monocyte-derived dendritic cells.

Cantharidin (CTD), a naturally occurring small molecule isolated from a medicinal insect, possesses anti-cancer and pro-inflammatory properties. We aimed to examine the effect of CTD on human myeloid dendritic cells (DCs) by examining immature DCs differentiated and maturated from CD14+ monocytes. CTD added into a culture of starting CD14+ monocytes markedly and dose-dependently reduced viability of harvested DC. Mature DCs differentiated in the presence of CTD had much fewer, shorter membranous projections than those without CTD. Changes in morphological features characteristic of necrotic cells were also evident. Furthermore, CTD affected DC differentiation and maturation phenotypes including down-regulation of surface CD1a, CD83 and DC-SIGN. DCs derived in the presence of CTD possessed an impaired allostimulatory activity on naive CD4+CD45+RA+T cell in terms of proliferation and interferon-γ production. It suggests that CTD may redirect DC differentiation toward a less mature stage and that this effect is not solely due to its cytotoxicity. Whether this effect refers to immune suppression or tolerance to disease treatments with unwanted immune reactions needs further evaluation.