Imaging the choreography of lymphocyte trafficking and the immune response

Abstract

The functioning of the immune system depends upon exquisitely choreographed interactions between its cellular constituents. Two-photon microscopy now enables us to visualize cell motility and cell-cell interactions deep within intact tissues and organs, both in explanted preparations and in vivo. Real-time immunoimaging techniques have illuminated the roles of random and chemokine-driven motility for cellular search strategies, the complex dynamics of cellular interactions, and the micro-anatomical localization and control of lymphocyte trafficking. Recently, advances have been made in these areas of research, as exemplified by studies investigating T cell-dendritic cell interactions, T cell-B cell interactions, and the regulation of lymphocyte egress from the lymph node.

Figure 1

Localization of different cell–cell interactions within a lymph node. The schematic shows T cells (T), B cells (B), dendritic cells (DC), lymphatic endothelial cells (LEC) and antigen. (a) Chemotaxis of B cells to the follicular border and interaction with helper T cells to form motile conjugate pairs. (b) Interaction of antigen-specific T cells with antigen-bearing dendritic cells within the T cell zone, leading to initial transient interactions and subsequent clusters, as illustrated here. (c) Regulation of T cell egress into medullary sinuses under basal conditions without antigen by stromal endothelial cells that constitute a barrier that can be closed by S1P₁ receptor agonists.