Fig. 2.

Characterization of the sender/receiver cell population. a Quantification of L-tryptophan production. HEK-293T cells with or without constitutively expressed TrpB (pHW074) were cultivated in InVitrus medium supplemented with 500 μM indole. Samples were taken at the indicated points in time and the L-tryptophan production was quantified in the culture medium. b Detection of interleukin-4. The sender/receiver cell population (without TrpB, pHW074) was cultivated in the presence of increasing concentrations of interleukin-4 for 48 h prior to quantification of the reporter yellow-fluorescent-protein (YFP). c Response to tryptophan and interleukin-4. HEK-293 T cells were transfected for interleukin-4-inducible SEAP production (pSTAT6 and pHW003) and then cultivated in InVitrus medium in the absence or presence of 50 μM L-tryptophan and 1 ng ml⁻¹ interleukin-4. After 48 h the production of the SEAP reporter was quantified in the culture medium. Data are means ± SD (n = 3)