DC under surveillance

Scientists have caught on film the activity of dermal dendritic cells as they encounter the protozoan parasite Leishmania.

Dendritic cells play a defensive role for the innate immune system in the skin, recognising foreign bodies and mobilising into the draining lymph nodes.

They are also suspected of presenting foreign antigens to T cells, although their behaviour is little understood.

To get a better idea of their behaviour, researchers from the Centenary Institute in Sydney put dermal dendritic cells under a two-photon microscope and watched as they came into contact with Leishmania major, the parasite that causes cutaneous Leishmaniasis.

What they saw was that dermal dendritic cells are normally very mobile under normal conditions, unlike their relatives in the epidermis. When confronted by Leishmania, however, they became completely immobile and began incorporating parasites into vacuoles.

The team, led by Professor Wolfgang Weninger, tracked the cells as they extended long, dynamic microtubules or pseudopods that engulfed the parasites and then retracted towards the cell body.

The team said the study, published in PLoS Pathogens, has uncovered a unique migratory tissue surveillance program to ensure rapid detection of pathogens.