Before revision:  Universality implies that if molecules are well mixed, this bifurcation should exhibit the critical scaling behavior of the Ising universality class in the mean-field limit. Making this statement quantitative requires the appropriate mapping between the biochemical parameters and the Ising parameters. Here we derive this mapping rigorously and uniquely for a broad class of stochastic birth-death models with feedback, and show that the expected static and dynamic critical exponents emerge. The generality of the mapping allows us to extract the order parameter, effective temperature, magnetic field,  and heat capacity from T cell flow cytometry data without needing to know the underlying molecular details.
After revision:  Universality implies that if molecules are well mixed, this bifurcation should exhibit the critical scaling behavior of the Ising universality class . In doing so, we derive a mapping of the biochemical parameters to an effective temperature, magnetic field, and heat capacity from T cell flow cytometry data without needing to know the underlying molecular details.