Close contact fluctuations: the seeding of signalling domains in the immunological synapse

We analyse the size and density of thermally induced regions of close contact in cell:cell contact interfaces within a harmonic potential approximation, estimating these regions to be below one-tenth of a micron across. Our calculations indicate that as the distance between the close contact threshold depth and the mean membrane-membrane separation increases, the density of close contact patches decreases exponentially while there is only a minimal variation in their mean size. The technique developed can be used to calculate the probability of first crossing in reflection symmetry violating systems.