Data-driven simulations elucidate how lymphocyte motility behaviors drive cell-cell interactions within germinal centers

Lymphocytes rely on cell motility to surveil immune microenvironments and engage in contact-mediated interactions with other cells as part of the adaptive immune response. Within the germinal center (GC) light zone, germinal center B-cells (GCBs) and T-follicular helper cells (Tfhs) engage in cell-cell interactions that enable antibody affinity maturation. The number and duration of GCB-Tfh interactions correlate with the success of the germinal center in effectively generating antibodies that can bind and neutralize antigens. Prior studies have shown that GCBs and Tfhs exploit distinct motility patterns to surveil the GC light zone and engage in these cell-cell interactions. However, the quantitative relationship between lymphocyte motility parameters (such as speed and tortuosity) and GCB-Tfh interactions has not been systematically explored. Here, we analyzed single-cell trajectories of GCBs and Tfhs from two-photon intravital microscopy videos of GCs within mouse popliteal lymph nodes. We found that these cells exhibit seven distinct motility behaviors, each with characteristic speeds and tortuosities. GCBs tended to move in slow and tortuous paths, while Tfhs adopted faster and more directed trajectories. We then developed a three-dimensional agent-based model (ABM) to simulate these experimentally-observed GCB and Tfh motility behaviors and predict their impact on GCB-Tfh interactions. Using the ABM, we found that the baseline motility behaviors of GCBs and Tfhs allow GCBs to maximize interactions with distinct Tfhs in a confined space.