"Two-photon imaging is going to change literally forever the way that we do biological science," said Witt, a developmental immunologist. "In the past, we'd take organs out, smush them up and basically do biochemistry in test tubes, or watch their behavior in a single layer of cells. It's an imaging revolution to be able to go into the native environment while keeping the intact organ alive and make movies of migrating cells."
With two-photon imaging, Witt and Robey identified thymus cells they dubbed beeliners moving nearly two centimeters - almost an inch - per hour, which is fast in the realm of cell movement. They think that these are cells that have received a signal committing them to be either a helper T cell - which aids other immune cells in fighting infections - or a killer T cell that seeks and destroys cells infected with virus.
On the other hand, uncommitted or immature T cells, what they call meanderers, wander slowly and apparently randomly around the outer layer, or cortex, of the thymus, perhaps in search of that life-altering signal.
Robey hopes to use two-photon imaging to investigate the signals responsible for changing these meanderers into purposeful beeliners that immediately leave the cortex for the interior medulla of the thymus.
"We're now at the point with this technology that we can begin to look at the movement of signaling molecules within the cells," she said.
Robey, with another colleague, Philippe Bousso, last year published a review in the journal Immunity describing the contributions two-photo imaging has made to the field. Robey and Witt publish their current study in the May 3 issue of the Public Library Of Science-Biology.
Two-photon imaging is a variation on the standard technique of labeling cells with fluorescent dye and then hitting them with a laser that makes
Source:University of California - Berkeley