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Dissertation defense, May 12: Jannatul Ferdous

May 9, 2025

Student Name: Jannatul Ferdous
Program: PhD Computer Science
Date: Monday, May 12th
Time: 11:00 am
Place: Zoom
Advisor: Dr. Melanie Moses

Title: "Exploring Immune System through Computational Modeling: A Comprehensive Study of Lymph Nodes and Immune Response Scaling, Vaccine Efficacy, and Large-Scale Extreme First Passage"

Abstract: The adaptive immune response is a complex, highly specific, memory-driven defense mechanism that develops over time to recognize and eliminate pathogens with remarkable precision and durability. This dissertation investigates the dynamics, scaling, and efficiency of the adaptive immune response through a synthesis of computational modeling, mathematical analysis, and agent-based simulations. First, we analyze the topology of the lymphatic network in mammals and investigate the T cell search time to find the lymph node that is containing the matching dendritic cell. Second, we show how the scaling of lymph node number and volume with body mass, leads to scale-invariant search times for T cells locating antigen-bearing dendritic cells across species. Third, we develop an analytical and numerical framework for extreme first passage time (EFPT) in confined three-dimensional volumes, revealing a transition from inverse-linear to inverse-logarithmic scaling of the fastest searcher’s discovery time as the number of searchers increases. This framework is validated against large-scale Monte Carlo simulations modeling T cells searching for a central target. Finally, we construct an agent-based model of B cell–mediated immunity to examine affinity maturation, antigenic drift, and vaccine efficacy against rapidly mutating viral variants. By representing receptors and epitopes in shape space and simulating somatic hypermuta- tion and clonal selection, our model predicts population dynamics of B cells, antibodies, and antigens over repeated exposures. Together, these studies elucidate fundamental principles of immune surveillance and response timing, with implications for translational vaccine design and broader applications in search theory, chemical kinetics, and complex systems.