Imaging Cytokine Concentration Fields Using PlaneView Imaging Devices.

We describe here a method to visualize concentration fields of cytokines around cytokine-secreting cells. The main challenge is that physiological cytokine concentrations can be very low, in the pico-molar range. Since it is currently impossible to measure such concentrations directly, we rely on cell's response to the cytokines-the phosphorylation of a transcription factor-that can be visualized through antibody staining. Our devices aim at mimicking conditions in dense tissues, such as lymph nodes. A small number of secreting cells is deposited on a polylysine-coated glass and covered by multiple layers of cytokine-consuming. The cells are left to communicate for 1 h, after which the top layers are removed and the bottom layer of cells is antibody labeled for the response to cytokines. Then a cross-section of cytokine fields can be visualized by standard fluorescence microscopy. This manuscript summarized our method to quantify the extent of cytokine-mediated cell-to-cell communications in dense collection of cells in vitro.