Nimmerjahn et al. have used the two-photon imaging technique to demonstrate the dynamic action of microglial cells in vivo. They were provided with a green fluorescent microglia cell line by S. Jung and D.R. Littman. In their elegantly illustrated paper, they provide living proof, by time-lapse imaging, of the way microglial cells are behaving in living brain. In the resting state, they are not at rest, but are continuously extending and retracting their processes over periods of minutes, sampling the extracellular environment, and generally patrolling their immediate environment. When the environment was disturbed, they immediately responded. This was done by either laser damage to microvessels, in which case the microglia moved to seal the leak, or with LPS injections from a micropipette, in which case the microglia engulfed the pipette tip. The three figures in the paper are supplemented by 12 short movies online. The movies need to be watched to grasp the full significance of the paper. This paper follows up a previous demonstration of the dynamic actions of astrocytes using...  Read more

Nimmerjahn et al. have used the two-photon imaging technique to demonstrate the dynamic action of microglial cells in vivo. They were provided with a green fluorescent microglia cell line by S. Jung and D.R. Littman. In their elegantly illustrated paper, they provide living proof, by time-lapse imaging, of the way microglial cells are behaving in living brain. In the resting state, they are not at rest, but are continuously extending and retracting their processes over periods of minutes, sampling the extracellular environment, and generally patrolling their immediate environment. When the environment was disturbed, they immediately responded. This was done by either laser damage to microvessels, in which case the microglia moved to seal the leak, or with LPS injections from a micropipette, in which case the microglia engulfed the pipette tip. The three figures in the paper are supplemented by 12 short movies online. The movies need to be watched to grasp the full significance of the paper. This paper follows up a previous demonstration of the dynamic actions of astrocytes using a comparable technique, but in which case it was mouse astrocytes that were transfected with fluorescent green (Mulligan et al., 2004). The most interesting experiment in this fascinating series is yet to come. That will be when neurons are transfected with fluorescent green and we will be able to witness the formation and retraction of synapses in real time.

View all comments by P.L. McGeer

This is really a breakthrough for Alzheimer's diesease research. I think this technique can be used for a variety of in vivo studies, e.g. to see how immune cells interact with target cells.

View all comments by Jun Xu