A coarse-grained view of biochemical feedback and cell-to-cell communication*

A ubiquitous way that cells share information is by sensing and secreting molecules. We consider this mechanism by developing a coarse-grained model of sense-and-secrete feedback. We first develop the theory of biochemical feedback at the single cell level, and then use this theory to investigate a model of two communicating cells. At the single cell level, we focus on an essential immune decision point: do I see something which is self or foreign? At steady state, near such a bifurcation, it is possible to map a class of models of feedback to the mean-field Ising model near the critical point. We use this mapping to analyze single-cell data and to consider the case of two communicating cells. We show that cell-to-cell molecule exchange induces a collective two-cell critical point and that the mutual information between the cells peaks at this critical point. Furthermore, information is subject to a trade-off: more information comes at the expense of slower collective dynamics. We conclude by discussing potential applications of our method to analyze experimental data.