Cutting edge: Clonally restricted production of the neurotrophins brain-derived neurotrophic factor and neurotrophin-3 mRNA by human immune cells andTh1/Th2-polarized expression of their receptors

Neurotrophins, such as neurotrophin-3 (NT-3) and brain-derived neurotrophic factor (BDNF), are potent regulators of neuronal functions. Here we show t hat human immune cells also produce NT-3 mRNA, secrete BDNF, and express th eir specific receptors trkB and trkC, The truncated trkB receptor, usually expressed in sensory neurons of the central nervous system, was also consti tutively expressed in unstimulated Th cells. Full-length trkB was detectabl e in stimulated PBMC, B cell lines, and Th1, but not in Th2 and Th0 cell cl ones. Clonally restricted expression was also observed for trkC, until now not detected on blood cells. The Th1 cytokine IL-2 stimulated production of trkB mRNA but not of trkC, whereas the Th2 cytokine IL-4 enhanced NT-3 but not BDNF mRNA expression. Microbial Ags, which influence the Th1/Th2 balan ce, could therefore modulate the neurotrophic system and thereby affect neu ronal synaptic activity of the central nervous system.