Interleukin-4 modulates the proliferation and differentiation of glial cells

We examined the effects of the T cell-derived cytokine, interleukin (IL)-4 on the proliferation and differentiation of C6 glial cells. IL-4 exerted a biphasic effect on cell proliferation, increasing cell proliferation at concentrations ranging from 10 to 50 ng/ml and inhibiting at higher concentrations. Inhibition of cell proliferation was associated with differentiation of the cells to express astrocytic phenotypes as evidenced by morphology, increased glial fibrillary acidic protein (GFAP) immunoreactivity and elevated glutamine synthetase expression. IL-4 also induced the secretion of nerve growth factor by these cells. These results suggest an important role for IL-4 during instances of CNS trauma and inflammation.