(568a) A Quantitative Analysis of Integrin Activation on T Cell Homing

T cell homing to sites of infection and inflammation is critical for the adaptive immune response and the maintenance of immune homeostasis. In addition, these cells must resist significant shear forces to exit the blood stream through the leukocyte adhesion cascade. T cells use selectin binding to slow down from the free stream velocity and integrin-ligand bonds to stop on the endothelial surface. Inspired by computation, we have measured the interdependence of the density of selectin, integrin ligand, and chemokines on the firm binding of T-cell under flow. Consistent with predictions, the results show that selectins and integrins act in synergy to support adhesion under flow (1). Now we have extended a previously published model that integrates intracellular signaling cascades into Adhesive Dynamics (2), which allows for the simulation of integrin activation upon leukocyte exposure to chemokine. Specifically, we have identified the role of the integrin activator proteins such as kindlin-3, which is absent in patients with the immune disorder Leukocyte Adhesion Deficiency Type 3. Our model makes several predictions regarding the quantitative effects of kindlin-3 deficiency, which are then tested through an experimental flow chamber with cells in which kindlin-3 is knocked down to confirm the critical role of kindlin-3 in supporting adhesion under flow.

References:

1. Anderson, N. R., Lee, D. & Hammer, D. A. An Experimentally Determined State Diagram for Human CD4⁺ T Lymphocyte CXCR4-Stimulated Adhesion Under Shear Flow. Cellular and Molecular Bioengineering 11, 91–98 (2018).
2. Beste, M. T., Lee, D., King, M. R., Koretzky, G. A. & Hammer, D. A. An Integrated Stochastic Model of “Inside-Out” Integrin Activation and Selective T-Lymphocyte Recruitment. Langmuir 28, 2225-2237 (2012).