Figure 1.

iDCs express three histamine receptors, and H1 is functionally active. (a) RT-PCR showing expression of histamine receptors H1, H2, and H3, and the GAPDH control in iDCs from three different donors. (b) Incubation of iDCs with histamine causes an increase in intracellular calcium that is blocked by an H1-specific antagonist. Fluo-3–loaded iDCs were preincubated at 0°C for 30 minutes with the indicated histamine receptor antagonist, warmed at 37°C for 1 minute, and at the time indicated by the arrow, stimulated with 10 μM histamine. Similar data were obtained with iDCs from two other donors. Antag, antagonist; Hist, histamine; MFI, mean fluorescence intensity.