Using a technique called two-photon laser- scanning microscopy (TPLSM) researchers can visualize, in three dimensions, the cellular waltzes by which the mammalian immune system develops and reacts to infection. The technique enables two low-energy photons to converge additively, exciting fluorophores only at the focal plane, which can be more than 300 µm beneath the surface of the tissue being examined.1 TPLSM represents a vast improvement over confocal laser techniques, which use single high-energy photons and cause photobleaching and phototoxicity, and cannot penetrate tissue. First pioneered in 1990, TPLSM began creeping into bio- logical research by mid-to-late decade; improvements to the reliability and usability of femtosecond lasers have now given it a permanent place.
Two recent forays represent the first time the technology has been used in immunological research. Michael Cahalan, professor of physiology and biophysics, University of California, Irvine, used the technology to track T and B cells in an ...
