Called two-photon laser-scanning microscopy, it has revealed, for example, the dramatic difference between the random wanderings of immature T cells and the goal-oriented, beeline movement of activated T cells.

"This is the first time anybody has quantitated four-dimensional data - spatial and time data - to get a picture of long-range cell migrations through tissue," said immunologist Ellen Robey, professor of immunology at the University of California, Berkeley. "The ability to directly visualize cells in living tissues has changed the way immunologists think about how cells explore their environment, how they signal to each other, and how they migrate."

Robey and post-doctoral colleague Colleen Witt are among a handful of researchers using two-photon imaging to obtain real-time images of cells throughout the top half-millimeter of a living organ, not just on the surface of tissue or within a slice.

"In our earlier studies (published in Science) we could see cells getting together, presumably signaling one another. In our current work, we observe cells that we believe have already gotten a signal beelining away," Robey said of her studies in the thymus, the immune system gland that weans baby T cells into activated helper, or CD4, cells and killer, or CD8, cells primed for combat with viral invaders. "We were surprised by how rapidly and directly the cells move to their final destination."

The technique could allow researchers in many fields of biology to track migrating cells, which biologists have discovered are common in many types of tissue, ranging from nerves to lymph nodes. To date, such long-range migrations have been inferred from observations of chemically fixed tissue at different stages of development.

"Two-photon imaging is going to change literally forever the way that we do biological science," said Wi
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Contact: Robert Sanders
rsanders@berkeley.edu
510-643-6998
University of California - Berkeley
3-May-2005