Antigen-Engaged B Cells Undergo Chemotaxis toward the T Zone and Form Motile Conjugates with Helper T Cells

TLDR

B‑cell and T‑cell interactions are crucial for antibody responses, yet their dynamics remain poorly understood. Using two‑photon microscopy, the study shows that antigen‑engaged B cells chemotax toward the B‑zone/T‑zone boundary via CCR7, initially slow but becoming highly motile (~9 µm/min) after one day, and form long‑lasting, highly dynamic conjugates with antigen‑specific helper T cells that migrate together, with B cells occasionally engaging multiple T cells while T cells remain monogamous, thereby providing in‑vivo evidence of lymphocyte chemotaxis and spatiotemporal dynamics in T‑cell‑dependent antibody responses.

Abstract

Interactions between B and T cells are essential for most antibody responses, but the dynamics of these interactions are poorly understood. By two-photon microscopy of intact lymph nodes, we show that upon exposure to antigen, B cells migrate with directional preference toward the B-zone-T-zone boundary in a CCR7-dependent manner, through a region that exhibits a CCR7-ligand gradient. Initially the B cells show reduced motility, but after 1 d, motility is increased to approximately 9 microm/min. Antigen-engaged B cells pair with antigen-specific helper T cells for 10 to more than 60 min, whereas non-antigen-specific interactions last less than 10 min. B cell-T cell conjugates are highly dynamic and migrate extensively, being led by B cells. B cells occasionally contact more than one T cell, whereas T cells are strictly monogamous in their interactions. These findings provide evidence of lymphocyte chemotaxis in vivo, and they begin to define the spatiotemporal cellular dynamics associated with T cell-dependent antibody responses.