AbstractSwelling of the lymph nodes is commonly observed during the adaptive immune response, yet its impacts on T cell trafficking and subsequent immune response are not well known. To better understand the effect of macro-scale alterations in the lymph node, we developed an agent-based model of the lymph node paracortex, describing T cell trafficking and response to antigen-presenting dendritic cells alongside swelling-induced changes in T cell recruitment and egress, and regulation of expression of egress-modulating T cell receptor Sphingosine-1-phosphate receptor-1. Validation of the model was achieved with in-silico replication of a range of published in-vivo and cell culture experiments. Analysis of CD4+ and CD8+ effector T cell response under varying swelling conditions showed that paracortical swelling aided initial T cell activation but could inhibit subsequent effector CD8+ T cell production if swelling occurs too early in the T cell proliferative phase. A global sensitivity analysis revealed that the effects of some parameters switch from aiding to inhibiting T cell response over a ten day response period. Furthermore, temporarily extending retention of newly differentiated effector T cells, mediated by Sphingosine-1-phosphate receptor-1 expression, mitigated some of the effects of early paracortical swelling. These results suggest that targeting the timing of lymph node swelling and temporary effector T cell retention may offer new ways to manipulate immune response.Author summaryWithin the lymph nodes the interaction of T cells and antigen presenting cells play a crucial role in initiating the adaptive immune response, resulting in effector T cells that travel to the infection site. Accompanying swelling of lymph nodes is commonly observed, yet the impact on T cell trafficking through the node and the subsequent immune response are not well known. We developed a novel agent-based model of a lymph node, describing immune response-induced expansion, contraction and changes in T cell recruitment and egress. We also describe the regulation of T cell expression of the Sphingosine-1-phosphate receptor-1, which is known to play an important role in T cell trafficking. We found that although swelling aids T cell activation, too early an increase in paracortical volume hinders the CD8+ effector T cell response. We also found that temporarily maintaining the down-regulation of Sphingosine-1-phosphate receptor-1 expression on newly differentiated effector T cells greatly increased the overall effector T cell output, and could counteract the loss in effector TC production due to early swelling. Our findings suggest that targeting the timing of lymph node swelling and temporary effector T cell retention may offer new ways to manipulate immune response.
The Initial Draining Lymph Node Primes the Bulk of the CD8 T Cell Response and Influences Memory T Cell Trafficking after a Systemic Viral Infection
