INTERLEUKIN-15, A T-CELL GROWTH-FACTOR, IS EXPRESSED IN HUMAN NEURAL CELL-LINES AND TISSUES

Interleukin-15 (IL-15) is a novel cytokine which shares activities and receptor components with IL-2. To investigate the biological roles of IL-15 in the human nervous system, we examined the expression of mRNA s for IL-15 and the IL-15 receptor three subunits (IL-15R alpha, IL-2R beta and IL-2R gamma) in human neural cell lines and tissues using re verse transcription-polymerase chain reaction and Southern blot analys is. The constitutive expression of high levels of IL-15 mRNA was obser ved in all the cell lines examined, including Y79 retinoblastoma, IMR- 32 neuroblastoma, SK-N-SH neuroblastoma, U-373MG glioma, KG-1-C glioma , NTera2 teratocarcinoma and neurons derived from NTera2 cells followi ng treatment with retinoic acid (RA). Among these cell lines, IL-15 pr otein was detectable at high levels in culture supernatants of SK-N-SH cells and NTera2-derived neurons. The expression of an alternatively- spliced transcript of the IL-15 gene was up-regulated in NTera2 cells during RA-induced neuronal differentiation, suggesting the existence o f differentiation-dependent transcriptional regulation. The expression of IL-15 mRNA was also identified in the human cerebral and cerebella r tissues, peripheral nerve and skeletal muscle, while the mRNAs for t he complete set of IL-15R components were detectable only in U-373MG c ells, cerebral and cerebellar tissues at significant levels. These res ults indicate that the expression of IL-15 but not of IL-15R mRNA is u niversal in human neural cell lines and tissues and raise the possibil ity that IL-15 acts as a neuroimmune regulatory factor in the human ce ntral nervous system. (C) 1998 Elsevier Science B.V.