L227	Intravital immunology: imaging T cell activation and effector function in vivo.
1T.R.Mempel, 2M.J.Pittet, 2K.Khazaie, 2H.von Boehmer, 1U.H.von Andrian
1CBR Institute for Biomedical Research and Department of Pathology, Harvard Medical School, Boston, US; 2Dana Faber Cancer Institute, Harvard Medical School, Boston, US.

Cell migration and cell-cell interaction are hallmarks of the function of the immune system. Recently, real-time in vivo imaging approaches have added a new dimension to our efforts to understand the dynamics and complex interplay of its different components in the steady state and during ongoing immune responses. In particular, multiphoton microscopy in conjunction with higher order harmonic generation imaging, have allowed a new perspective by permitting prolonged observation of dynamic events occuring hundreds of micrometers within solid tissues of live animals. Using a recently developed model of intravital multiphoton microscopy of murine lymph nodes we have previously described the kinetics of antigenic priming of naive CD8+ T cells by dendritic cells as a three-phase process, involving distinct stages of dynamics of cellular interaction. More recently, we have started to study cytolytic effector function of cytotoxic T cells during their interaction with antigen-pulsed B cells. Preliminary observations from these experiments will be discussed.

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