Fig. 7. mAb16-39 induces neurite outgrowth in an ERK-dependent manner. SK-N-SH cells were cultured in insulin, transferrin and selenium-supplemented media in the presence of mAb16-39 (4 nM), control normal rat IgG (4 nM), or NGF (2 nM) and photographed at day 2.5. Treatment of cells with mAb16-39 (C) resulted in extensive outgrowth of long neurites and increased cell number. Similar but less significant effects were observed in cells treated with NGF (B). Cells treated with control IgG (A) showed no significant effect on morphology. Neurite extension induced by mAb16-39 was efficiently blocked by the MEK inhibitor PD98059 (50 µM) (D). Scale bar, 50 µm. (E) Cell differentiation was scored as described in Materials and Methods and expressed as the mean±s.e.m. (%).