Abstract

Many lymphocyte functions, such as antigen recognition, take place deep in densely populated lymphoid organs. Because direct in vivo observation was not possible, the dynamics of immune-cell interactions have been inferred or extrapolated from in vitro studies. Two-photon fluorescence excitation uses extremely brief (<1 picosecond) and intense pulses of light to 'see' directly into living tissues, to a greater depth and with less phototoxicity than conventional imaging methods. Two-photon microscopy, in combination with newly developed indicator molecules, promises to extend single-cell approaches to the in vivo setting and to reveal in detail the cellular collaborations that underlie the immune response.

Author affiliations

1. Departments of Physiology and Biophysics, University of California, Irvine, California 92697-4561, USA.
2. Department of Neurobiology and Behavior, University of California, Irvine, California 92697-4561, USA.

Correspondence to: Michael D. Cahalan¹ Email: mcahalan@uci.edu