CD209 and infection: Using in vitro blood MDDCs, it has been shown to bind HIV in a tetrameric form59 and to play a role in the formation of the MHC-II-independent60 infectious synapse between DCs and T cells,61,62 whereby HIV is transferred to T cells in a protected environment while the cells are connected.63 Binding of HIV to DC-SIGN on these model cells triggers a signalling cascade that enhances trans-infection.64 Many studies have shown that tissue DC-SIGN expressing cells efficiently take up and transmit HIV.65–68