CD4 and infection: For the trans-infection of HIV via MDDCs, early imaging studies showed that, similar to what occurs during T cell–T cell transmission, viral particles are concentrated on DC at the site of contact, CD4 and chemokine co-receptors are recruited to the contact site on the T cell surface, and virions are transferred to T cells (McDonald et al., 2003; Arrighi et al., 2004; Turville et al., 2004; Garcia et al., 2005; Wang et al., 2007).