Immune responses involve cell-cell interactions within lymphoid tissues, trafficking of activated cells to sites of effector function, and the migration of such effector cells within peripheral tissues. To gain a more detailed appreciation of the relationships among cell movement, tissue architecture, and immune function, we have used intravital multiphoton microscopy and a novel multiplex immunohistochemical method to analyze immune cell dynamics and tissue micro-anatomy.
Our data show that migrating T cells follow stromal pathways in lymph nodes, which enhances interactions with dendritic cells. Additional chemokine cues facilitate interactions among rare antigen-presenting and antigen-recognizing cells, with the strength of these interactions as assessed by Ca2+ imaging dictating the polarization of the ensuing effector T cell response. In tissue sites, effector cells stop when they perceive antigen and undergo transient activation and polarized cytokine release, followed by tuning of their response to existing antigen levels. Innate immune (neutrophil) responses have been dissected at the molecular level. The role of cell localization in both innate and adaptive immunity has also been addressed using a new method called histo-cytometry that reveals at high resolution the spatial positioning and activation state of cells with complex phenotypes in tissues. These observations show the power of in situ imaging in the acquisition of a more accurate picture of the molecular, cellular, spatial, and temporal aspects of cell function and signaling events in host immune responses.
This work was supported in part by the Intramural Research Program of the NIH, NIAID.