THE cytokine IFN-γ was shown to regulate growth and differentiation of human embryonic forebrain astrocytes. This work investigated a signalling pathway used by IFN-γ during the process of growth regulation of human fetal astrocytes obtained from first trimester embryos. IFN-γ induced significantly higher cell survival compared to that of unexposed cultures, and this survival could be suppressed by incubation with the tyrosine protein kinase (TPK) specific inhibitor tyrphostin A47 at the non-toxic concentration of 10-6M. The signal transducer and activator of transcription (STAT)-1 was translocated into the nucleus upon IFN-γ stimulation, which was also blocked by incubation with A47. Our data demonstrate that TPKs are actively involved in growth regulation of the developing brain astrocytes induced by IFN-γ.