SIGLEC6 and preeclampsia: Given that Siglec6 is to be found only in human placenta and preeclampsia is regarded as a uniquely human disease [90], the molecular roles of Siglec6 in villous cytotrophoblasts and syncytiotrophoblasts, and in extravillous cytotrophoblasts, in association with leptin, warrant further and deep investigations, in context of invasion process of cytotrophoblasts and immune defense response in decidua.