FACscan analysis of expression of RFP in 3 independent clones in the CL [pTcrRNA-T7tetR] background. Tetracycline (0.5 μg ml-1) was added and samples were removed and fixed after 6 days. The level of fluorescence in the population was measured by counting 5 × 103 cells per timepoint. The filled area indicates the uninduced cells, while the green line represents the induced population. The Y axis indicates the number of cells counted, whilst the X axis shows the level of fluorescence in AFU.