Cited research Proc. Natl Acad. Sci. USA doi:10.1073/pnas.1003040107 (2010)

One route HIV takes to infecting the immune system's T cells is through dendritic cells, which present antigen on their surface. Researchers have captured three-dimensional images of single viral particles being transmitted between the two cell types (pictured, T cell in green).

Sriram Subramaniam at the National Institutes of Health in Bethesda, Maryland, and his co-workers used three-dimensional electron microscopy to show that the surface membrane of the dendritic cell first extends and, like a veil, envelops the T cell. This provides a protected area in which the membranes of the two cells form protrusions that come together like interlocking fingers. Viral particles are seen at the tips and along the T-cell protrusions. The T cells' CD4 receptors mediate HIV transmission.

This shielding of T cells at these junctions could limit the ability of HIV-neutralizing antibodies to block T-cell infection.