Dendritic cells take up invading pathogens and other antigens, process them and present them to T cells. In the 1 May issue of Sciencexpress, David McDonald et al. report that HIV exploits this function to infect more T cells, its primary target.

Credit: Courtesy of Dave McDonald and Tom Hope

Dendritic cells take up HIV particles and gather them in protected vesicles. The investigators found that when a dendritic cell (left; see Supplementary Movie 1 online) meets a target cell (right; DNA in blue and actin in red), the virus particles (green) scattered around the dendritic cell mobilize and cluster along the contact surface between the two cells. At the same time, HIV receptors also travel to the contact site. The flurry of activity at the interface enables some of the HIV particles to cross the divide into the target cell as shown here. The target cell in this image is a fibroblast transfected with the HIV receptor CD4 and its coreceptor CXCR4; the authors noted similar behavior using T cells as the targets.

The authors propose that HIV takes advantage of the large surface area of dendritic cells to get as many particles taken up as possible and then concentrate them at the interface with the target cell, thereby increasing the chance of productive T-cell infection. Recent studies with other pathogens suggest that this exploitation may be fairly widespread, say the authors.