Universality of biochemical feedback and its application to immune cells

Biochemical feedback can lead to a bifurcation in cellular state space. For well-mixed systems, this transition should exhibit the critical scaling exponents of the Ising universality class in the mean-field limit. Here, we rigorously derive a mapping between a broad class of of biochemical feedback models and the mean-field Ising model, and show that the expected critical scaling exponents emerge. The generality of this mapping allows us to extract the order parameter, effective reduced temperature, magnetic field, and heat capacity from T cell flow cytometry data. We find that T cells obey critical scaling relations and exhibit critical slowing down. We also identify the dynamic critical exponents of the system, and show that our nonequilibrium feedback models exhibit the Kibble-Zurek collapse of critical physical systems.