Fig. (1) Cytokines induce apoptosis of human fetal lung epithelial cells. (A) Electron Microscopy of immature and mature human fetal lung epithelial cells incubated with or without cytokines for 24 hours. The presence of abundant multi-vesicular bodies differentiates immature from mature human fetal lung epithelial cells. Nuclear (white arrows) and cytoplasmic (black arrows) condensation present in cytokine-stimulated immature and mature human fetal lung epithelial cells (bar=10µm). (B) Percentage of cell death in immature and mature human fetal lung epithelial cells upon cytokine exposure. Cytokine exposure resulted in an increase in cell death in immature human fetal lung epithelial cells and in mature human fetal lung epithelial cells at 24 and 48 hours (*p<0.05). Cytokine-exposed immature cells had a more rapid and increased degree of cell death compared to cytokine-exposed mature cells (#p<0.01).