Reported expression of 5-HT receptor transcripts in immune cells. Synthesis of findings from studies by *León-Ponte et al in this issue of Blood and from Stefulj et al,3 Idzko et al,4 and Durk et al5 highlighting the repertoire of 5-HT receptor subtype of mRNA expressed in immune cells. R indicates resting; A, activated; I, immature; M, mature; Ion chan., ligand-gated ion channel; −, negative; +, strong signal; and ±, weak signal. §5-HT1B protein increased on activation. ¶Absent from mouse and rat. #Truncated transcript in human. Illustration by Frank Forney.