UBC Math Bio Seminar: Debraj Ghose

Immune cells perform exquisite feats of collective organization, assembling into tissues that can shapeshift to meet functional demands. Dispersed, gas-like immune cells surveil tissues for threats; liquid-like germinal centers enable the rapid cellular rearrangements needed for antibody evolution; and solid-like granulomas wall off pathogens that cannot be cleared. Traditional immunology has made tremendous progress by dissecting molecular pathways, receptor identities, and chemical signals. Yet the physical principles that govern how immune tissues tune their material properties remain largely unexplored. I am interested in understanding this physical dimension of immunity: how individual cells act as agents that process information, and how interactions among these agents give rise to emergent tissue dynamics. In this talk, I will present recent work demonstrating that the physical state of immune tissue is chemically programmable. Using agent-based modeling, we show that tissue fluidity is a key control parameter for B cell evolution in germinal centers. Experimentally, we find that CD40L-stimulated human B cells self-organize into active, liquid-like condensates, and that T follicular helper cytokines IL-4 and IL-21 tune this effective temperature, driving transitions from cohesive liquid-like states to dispersed gas-like morphologies. These findings reveal a biophysical axis of immune regulation and suggest new strategies for engineering and harnessing collective immune function.